also be negative. The procedure that follows deletes rows 2, 4, 6, 8, and 10 of the active worksheet:
Sub DeleteRows() Dim RowNum As Long For RowNum = 10 To 2 Step -2 Rows(RowNum).Delete Next RowNum End Sub
You may wonder why we used a negative Step value in the DeleteRows procedure. If you use a positive Step value, as shown in the following procedure, incorrect rows are deleted. That's because the rows below a deleted row get a new row number. For example, when row 2 is deleted, row 3 becomes the new row 2. Using a negative Step value ensures that the correct rows are deleted.
Sub DeleteRows2() Dim RowNum As Long For RowNum = 2 To 10 Step 2 Rows(RowNum).Delete Next RowNum End Sub
The following procedure performs the same task as the BadLoop example at the beginning of the “Looping blocks of instructions” section. We eliminate the GoTo statement, however, converting a bad loop into a good loop that uses the For-Next structure.
Sub GoodLoop() Dim StartVal As Integer Dim NumToFill As Integer Dim iCount As Integer StartVal = 1 NumToFill = 100 For iCount = 0 To NumToFill - 1 ActiveCell.Offset(iCount, 0).Value = StartVal + iCount Next iCount End Sub
For-Next loops can also include one or more Exit For statements in the loop. When this statement is encountered, the loop terminates immediately, and control passes to the statement following the Next statement of the current For-Next loop. The following example demonstrates the use of the Exit For statement. This procedure determines which cell has the largest value in Column A of the active worksheet:
Sub ExitForDemo() Dim MaxVal As Double Dim Row As Long MaxVal = Application.WorksheetFunction.Max(Range("A:A")) For Row = 1 To 1048576 If Cells(Row, 1).Value = MaxVal Then Exit For End If Next Row MsgBox "Max value is in Row " & Row Cells(Row, 1).Activate End Sub
The maximum value in the column is calculated by using the Excel MAX function, and the value is assigned to the MaxVal variable. The For-Next loop checks each cell in the column. If the cell being checked is equal to MaxVal, the Exit For statement terminates the loop, and the statements following the Next statement are executed. These statements display the row of the maximum value and activate the cell.
NOTE
The ExitForDemo procedure is presented to demonstrate how to exit from a For-Next loop. However, it's not the most efficient way to activate the largest value in a range. In fact, a single statement does the job.
Range("A:A").Find(Application.WorksheetFunction.Max _ (Range("A:A"))).Activate
The previous examples use relatively simple loops. But you can have any number of statements in the loop, and you can even nest For-Next loops inside other For-Next loops. Here's an example that uses nested For-Next loops to initialize a 10 × 10 × 10 array with the value –1. When the procedure is finished, each of the 1,000 elements in MyArray contains –1.
Sub NestedLoops() Dim MyArray(1 to 10, 1 to 10, 1 to 10) Dim i As Integer, j As Integer, k As Integer For i = 1 To 10 For j = 1 To 10 For k = 1 To 10 MyArray(i, j, k) = -1 Next k Next j Next i ' [More code goes here] End Sub
Do While loops
This section describes another type of looping structure available in VBA. Unlike a For-Next loop, a Do While loop executes as long as a specified condition is met.
A Do While loop can have either of two syntaxes. Here's the first:
Do [While condition] [instructions] [Exit Do] [instructions] Loop
Here's the second:
Do [instructions] [Exit Do] [instructions] Loop [While condition]
As you can see, VBA lets you put the While condition at the beginning or the end of the loop. The difference between these two syntaxes involves the point at which the condition is evaluated. In the first syntax, the contents of the loop may never be executed. In the second syntax, the statements inside the loop are always executed at least one time.
The following examples insert a series of dates into the active worksheet. The dates correspond to the days in the current month, and the dates are entered in a column beginning at the active cell.
NOTE
These examples use some VBA date-related functions:
Date returns the current date.
Month returns the month number for a date supplied as its argument.
DateSerial returns a date for the year, month, and day supplied as arguments.
The first example demonstrates a Do While loop that tests the condition at the beginning of the loop: The EnterDates1 procedure writes the dates of the current month to a worksheet column, beginning with the active cell.
Sub EnterDates1() ' Do While, with test at the beginning Dim TheDate As Date TheDate = DateSerial(Year(Date), Month(Date), 1) Do While Month(TheDate) = Month(Date) ActiveCell = TheDate TheDate = TheDate + 1 ActiveCell.Offset(1, 0).Activate Loop End Sub
This procedure uses a variable, TheDate, which contains the dates that are written to the worksheet. This variable is initialized with the first day of the current month. Inside the loop, the value of TheDate is entered into the active cell, TheDate is incremented, and the next cell is activated. The loop continues while the month of TheDate is the same as the month of the current date.
The following procedure has the same result as the EnterDates1 procedure, but it uses the second Do While loop syntax, which checks the condition at the end of the loop.
Sub EnterDates2() ' Do While, with test at the end Dim TheDate As Date TheDate = DateSerial(Year(Date), Month(Date), 1) Do ActiveCell = TheDate TheDate = TheDate + 1 ActiveCell.Offset(1, 0).Activate Loop While Month(TheDate) = Month(Date) End Sub
Do While loops can also contain one or more Exit Do statements. When an Exit Do statement is encountered, the loop ends immediately, and control passes to the statement following the Loop statement.
Do Until loops
The Do Until loop structure is similar to the Do While structure. The difference is evident only when the condition is tested. In a Do While loop, the loop executes while the condition is True; in a Do Until loop, the loop executes until the condition is True.
Do Until also has two syntaxes. Here's the first way:
Do [Until condition] [instructions] [Exit Do] [instructions] Loop
Here's the second way:
Do
