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Another procedure that involves decision making is looping. Excel VBA allows a procedure to be repeated many times until a condition or a set of conditions is fulfilled. This is generally called looping . Looping is a very useful feature of Excel VBA because it makes repetitive works easier. There are two kinds of loops in Visual Basic, the For…….Next loop, the While….Wend loop and the the Do…Loop . We shall deal with the For………Next loop and the While….Wend loop first and we will deal with the Do….Loop in the next lesson.
14.1 One level For…..Next Loop
The one level For….Next Loop event procedure is written as follows:
For counter=startNumber to endNumber (Step increment)
One or more VB statements
Next
Example 14.1
In this Excel VBA program, you place the command button 1 on the spreadsheet then click on it to go into the Visual Basic editor. When you click on the button, the Excel VBA program will fill cells(1,1) with the value of 1, cells(2,1) with the value of 2, cells(3,1) with the value of 3……until cells (10,1) with the value of 10. The position of each cell in the Excel spreadsheet is referenced with cells(i,j), where i represents row and j represent the column.
The Code
Private Sub CommandButton1_Click()
Dim i As Integer
For i = 1 To 10
Cells(i, 1).Value = i
Next
End Sub
The Output is shown in Figure 5.1
Figure 14.1
Example 14.2
For……..Next loop with step increments. In this example, the number increases by 2 at a time. The resulting series is 1,3,5,7,9 displayed in Cells(1,1), Cells(3,1),Cells(5,1), Cells(7,1) and Cells(9,1) respectively.
The code
Private Sub CommandButton1_Click()
Dim i As Integer
For i = 1 To 10 Step 2
Cells(i, 1).Value = i
Next
End Sub
The Output
Figure 14.2
14.2 Nested For….Next Loops
Nested For…….Next loops mean there are more than one For…Next Loops are nested within the first level For…..Next loop. The structure is as follows:
For counter=startNumber1 to endNumber1
For counter=startNumber2 to endNumber2
For counter=startNumber3 to endNumber3
One or more VB statements
Next
Next
Next
Example 14.3
In this example , we use nested loop to put the values of i+j from cells(1,1),cells(1,2),cells(1,3),cells(1,4),cells(1,5) ……….until cells(10,5). The code and output are shown below.
Private Sub CommandButton1_Click()
Dim i, j As Integer
For i = 1 To 10
For j = 1 To 5
Cells(i, j).Value = i + j
Next
Next
End Sub
The Output
 Figure 14.3 |
14.3 While….Wend Loop
The structure of a While….Wend Loop is very similar to the Do Loop. it takes the following form:
While condition
Statements
Wend
The above loop means that while the condition is not met, the loop will go on. The loop will end when the condition is met. Let’s examine the program listed in example 14.4.
Example 14.4
In this example, the Excel VBA program will compute the square of numbers from 1 to 15 and displays them from Cells(1,1) to Cells(15,1)
The Code
Private Sub CommandButton1_Click()
Dim i As Integer
i = 1
While i <= 15
Cells(i, 1) = i ^ 2
i = i + 1
Wend
End Sub
The Output
Figure 14.4
