Create a Macro
With Excel VBA you can automate tasks in Excel by writing so called macros. In this chapter, learn how to create a simple macro which will be executed after clicking on a command button. First, turn on the Developer tab.
Developer Tab
To turn on the Developter tab, execute the following steps.
1. Right click anywhere on the ribbon, and then click Customize the Ribbon.
2. Under Customize the Ribbon, on the right side of the dialog box, select Main tabs (if necessary).
3. Check the Developer check box.
4. Click OK.
5. You can find the Developer tab next to the View tab.
Command Button
To place a command button on your worksheet, execute the following steps.
1. On the Developer tab, click Insert.
2. In the ActiveX Controls group, click Command Button.
3. Drag a command button on your worksheet.
Assign a Macro
To assign a macro (one or more code lines) to the command button, execute the following steps.
1. Right click CommandButton1 (make sure Design Mode is selected).
2. Click View Code.
The Visual Basic Editor appears.
3. Place your cursor between Private Sub CommandButton1_Click() and End Sub.
4. Add the code line shown below.
Note: the window on the left with the names Sheet1, Sheet2 and Sheet3 is called the Project Explorer. If the Project Explorer is not visible, click View, Project Explorer. To add the Code window for the first sheet, click Sheet1 (Sheet1).
5. Close the Visual Basic Editor.
6. Click the command button on the sheet (make sure Design Mode is deselected).
Result:
Congratulations. You've just created a macro in Excel!
Visual Basic Editor
To open the Visual Basic Editor, on the Developer tab, click Visual Basic.
The Visual Basic Editor appears.
MsgBox
The MsgBox is a dialog box in Excel VBA you can use to inform the users of your program. Place a command button on your worksheet and add the following code lines:
1. A simple message.
MsgBox "This is fun"
Result when you click the command button on the sheet:
2. A little more advanced message. First, enter a number into cell A1.
MsgBox "Entered value is " & Range("A1").Value
Result when you click the command button on the sheet:
Note: we used the & operator to concatenate (join) two strings. Although Range("A1").value is not a string, it works here.
3. To start a new line in a message, use vbNewLine.
MsgBox "Line 1" & vbNewLine & "Line 2"
Result when you click the command button on the sheet:
Workbook and Worksheet Object
Learn more about the Workbook and Worksheet object in Excel VBA.
Object Hierarchy
In Excel VBA, an object can contain another object, and that object can contain another object, etc. In other words, Excel VBA programming involves working with an object hierarchy. This probably sounds quite confusing, but we will make it clear.
The mother of all objects is Excel itself. We call it the Application object. The application object contains other objects. For example, the Workbook object (Excel file). This can be any workbook you have created. The Workbook object contains other objects, such as the Worksheet object. The Worksheet object contains other objects, such as the Range object.
The Create a Macro chapter illustrates how to run code by clicking on a command button. We used the following code line:
Range("A1").Value = "Hello"
but what we really meant was:
Application.Workbooks("create-a-macro").Worksheets(1).Range("A1").Value = "Hello"
Note: the objects are connected with a dot. Fortunately, we do not have to add a code line this way. That is because we placed our command button in create-a-macro.xls, on the first worksheet. Be aware that if you want to change things on different worksheets, you have to include the Worksheet object. Read on.
Collections
You may have noticed that Workbooks and Worksheets are both plural. That is because they are collections. The Workbooks collection contains all the Workbook objects that are currently open. The Worksheets collection contains all the Worksheet objects in a workbook.
You can refer to a member of the collection, for example, a single Worksheet object, in three ways.
1. Using the worksheet name.
Worksheets("Sales").Range("A1").Value = "Hello"
2. Using the index number (1 is the first worksheet starting from the left).
Worksheets(1).Range("A1").Value = "Hello"
3. Using the CodeName.
Sheet1.Range("A1").Value = "Hello"
To see the CodeName of a worksheet, open the Visual Basic Editor. In the Project Explorer, the first name is the CodeName. The second name is the worksheet name (Sales).
Note: the CodeName remains the same if you change the worksheet name or the order of your worksheets so this is the safest way to reference a worksheet. Click View, Properties Window to change the CodeName of a worksheet. There is one disadvantage, you cannot use the CodeName if you reference a worksheet in a different workbook.
Properties and Methods
Now let's take a look at some properties and methods of the Workbooks and Worksheets collection. Properties are something which an collection has (they describe the collection), while methods do something (they perform an action with an collection).
Place a command button on your worksheet and add the code lines:
1. The Add method of the Workbooks collection creates a new workbook.
Workbooks.Add
Note: the Add method of the Worksheets collection creates a new worksheet.
2. The Count property of the Worksheets collection counts the number of worksheets in a workbook.
MsgBox Worksheets.Count
Result when you click the command button on the sheet:
Note: the Count property of the Workbooks collection counts the number of active workbooks.
Range Object
The Range object, which is the representation of a cell (or cells) on your worksheet, is the most important object of Excel VBA. This chapter gives an overview of the properties and methods of the Range object. Properties are something which an object has (they describe the object), while methods do something (they perform an action with an object). Range ExamplesPlace a command button on your worksheet and add the following code line: Range("B3").Value = 2 Result when you click the command button on the sheet: Code: Range("A1:A4").Value = 5 Result: Code: Range("A1:A2,B3:C4").Value = 10 Result: Note: to refer to a named range in your Excel VBA code, use a code line like this: Range("Prices").Value = 15 CellsInstead of Range, you can also use Cells. Using Cells is particularly useful when you want to loop through ranges. Code: Cells(3, 2).Value = 2 Result: Explanation: Excel VBA enters the value 2 into the cell at the intersection of row 3 and column 2. Code: Range(Cells(1, 1), Cells(4, 1)).Value = 5 Result: Declare a Range ObjectYou can declare a Range object by using the keywords Dim and Set. Code: Dim example As Range Set example = Range("A1:C4") example.Value = 8 Result: SelectAn important method of the Range object is the Select method. The Select method simply selects a range. Code: Dim example As Range Set example = Range("A1:C4") example.Select Result: RowsThe Rows property gives access to a specific row of a range. Code: Dim example As Range Set example = Range("A1:C4") example.Rows(3).Select Result: Note: border for illustration only. ColumnsThe Columns property gives access to a specific column of a range. Code: Dim example As Range Set example = Range("A1:C4") example.Columns(2).Select Result: Note: border for illustration only. Copy/PasteThe Copy and Paste method are used to copy a range and to paste it somewhere else on the worksheet. Code: Range("A1:A2").Select Selection.Copy Range("C3").Select ActiveSheet.Paste Result: Although this is allowed in Excel VBA, it is much better to use the code line below which does exactly the same. Range("C3:C4").Value = Range("A1:A2").Value ClearTo clear the content of an Excel range, you can use the ClearContents method. Range("A1").ClearContents or simply use: Range("A1").Value = "" Note: use the Clear method to clear the content and format of a range. Use the ClearFormats method to clear the format only. CountWith the Count property, you can count the number of cells, rows and columns of a range. Note: border for illustration only. Code: Dim example As Range Set example = Range("A1:C4") MsgBox example.Count Result: Code: Dim example As Range Set example = Range("A1:C4") MsgBox example.Rows.Count Result: Note: in a similar way, you can count the number of columns of a range. VariablesThis chapter teaches you how to declare, initialize and display a variable in Excel VBA. Letting Excel VBA know you are using a variable is called declaring a variable. Initializing simply means assigning a beginning (initial) value to a variable. Place a command button on your worksheet and add the code lines below. To execute the code lines, click the command button on the sheet. IntegerInteger variables are used to store whole numbers. Dim x As Integer x = 6 Range("A1").Value = x Result: Explanation: the first code line declares a variable with name x of type Integer. Next, we initialize x with value 6. Finally, we write the value of x to cell A1. StringString variables are used to store text. Code: Dim book As String book = "bible" Range("A1").Value = book Result: Explanation: the first code line declares a variable with name book of type String. Next, we initialize book with the text bible. Always use apostrophes to initialize String variables. Finally, we write the text of the variable book to cell A1. DoubleA variable of type Double is more accurate than a variable of type Integer and can also store numbers after the comma. Code: Dim x As Integer x = 5.5 MsgBox "value is " & x Result: But that is not the right value! We initialized the variable with value 5.5 and we get the value 6. What we need is a variable of type Double. Code: Dim x As Double x = 5.5 MsgBox "value is " & x Result: Note: Long variables have even larger capacity. Always use variables of the right type. As a result, errors are easier to find and your code will run faster. BooleanUse a Boolean variable to hold the value True or False. Code: Dim continue As Boolean continue = True If continue = True Then MsgBox "Boolean variables are cool" Result: Explanation: the first code line declares a variable with name continue of type Boolean. Next, we initialize continue with the value True. Finally, we use the Boolean variable to only display a MsgBox if the variable holds the value True. If Then StatementUse the If Then statement in Excel VBA to execute code lines if a specific condition is met. If Then StatementPlace a command button on your worksheet and add the following code lines: Dim score As Integer, result As String score = Range("A1").Value If score >= 60 Then result = "pass" Range("B1").Value = result Explanation: if score is greater than or equal to 60, Excel VBA returns pass. Result when you click the command button on the sheet: Note: if score is less than 60, Excel VBA places the value of the empty variable result into cell B1. Else StatementPlace a command button on your worksheet and add the following code lines: Dim score As Integer, result As String score = Range("A1").Value If score >= 60 Then result = "pass" Else result = "fail" End If Range("B1").Value = result Explanation: if score is greater than or equal to 60, Excel VBA returns pass, else Excel VBA returns fail. Result when you click the command button on the sheet: Note: only if you have one code line after Then and no Else statement, it is allowed to place a code line directly after Then and to omit (leave out) End If (first example). Otherwise start a new line after the words Then and Else and end with End If (second example). LoopLooping is one of the most powerful programming techniques. A loop in Excel VBA enables you to loop through a range of cells with just a few codes lines. Single LoopYou can use a single loop to loop through a one-dimensional range of cells. Place a command button on your worksheet and add the following code lines: Dim i As Integer For i = 1 To 6 Cells(i, 1).Value = 100 Next i Result when you click the command button on the sheet: Explanation: The code lines between For and Next will be executed six times. For i = 1, Excel VBA enters the value 100 into the cell at the intersection of row 1 and column 1. When Excel VBA reaches Next i, it increases i with 1 and jumps back to the For statement. For i = 2, Excel VBA enters the value 100 into the cell at the intersection of row 2 and column 1, etc. Note: it is good practice to always indent (tab) the code between the words For and Next. This makes your code easier to read. Double LoopYou can use a double loop to loop through a two-dimensional range of cells. Place a command button on your worksheet and add the following code lines: Dim i As Integer, j As Integer For i = 1 To 6 For j = 1 To 2 Cells(i, j).Value = 100 Next j Next i Result when you click the command button on the sheet: Explanation: For i = 1 and j = 1, Excel VBA enters the value 100 into the cell at the intersection of row 1 and column 1. When Excel VBA reaches Next j, it increases j with 1 and jumps back to the For j statement. For i = 1 and j = 2, Excel VBA enters the value 100 into the cell at the intersection of row 1 and column 2. Next, Excel VBA ignores Next j because j only runs from 1 to 2. When Excel VBA reaches Next i, it increases i with 1 and jumps back to the For i statement. For i = 2 and j = 1, Excel VBA enters the value 100 into the cell at the intersection of row 2 and column 1, etc. Triple LoopYou can use a triple loop to loop through two-dimensional ranges on multiple Excel worksheets. Place a command button on your worksheet and add the following code lines: Dim c As Integer, i As Integer, j As Integer For c = 1 To 3 For i = 1 To 6 For j = 1 To 2 Worksheets(c).Cells(i, j).Value = 100 Next j Next i Next c Explanation: The only change made compared to the code for the double loop is that we have added one more loop and added Worksheets(c). in front of Cells to get the two-dimensional range on the first sheet for c = 1, the second sheet for c = 2 and the third sheet for c = 3. Download the Excel file to see this result. Do While LoopBesides the For Next loop, there are other loops in Excel VBA. For example, the Do While Loop. Code placed between Do While and Loop will be repeated as long as the part after Do While is true. 1. Place a command button on your worksheet and add the following code lines: Dim i As Integer i = 1 Do While i < 6 Cells(i, 1).Value = 20 i = i + 1 Loop Result when you click the command button on the sheet: Explanation: as long as i is lower than 6, Excel VBA enters the value 20 into the cell at the intersection of row i and column 1 and increments i by 1. In Excel VBA (and in other programming languages), the symbol '=' means becomes. It does not mean equal. So i = i + 1 means i becomes i + 1. In other words: take the present value of i and add 1 to it. For example, if i = 1, i becomes 1 + 1 = 2. As a result, the value 20 will be placed into column A five times (not six because Excel VBA stops when i equals 6). 2. Enter some numbers in column A. 3. Place a command button on your worksheet and add the following code lines: Dim i As Integer i = 1 Do While Cells(i, 1).Value <> "" Cells(i, 2).Value = Cells(i, 1).Value + 10 i = i + 1 Loop Result when you click the command button on the sheet: Explanation: as long as Cells(i, 1).Value is not empty (<> means not equal to), Excel VBA enters the value into the cell at the intersection of row i and column 2, that is 10 higher than the value in the cell at the intersection of row i and column 1. Excel VBA stops when i equals 7 because Cells(7, 1).Value is empty. This is a great way to loop through any number of rows on a worksheet. Macro Errors
|
No comments:
Post a Comment