Michael Alexander - Excel 2019 Power Programming with VBA

The following procedure has the same result as the EnterDates1procedure, but it uses the second Do Whileloop 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 Whileloops can also contain one or more Exit Dostatements. When an Exit Dostatement is encountered, the loop ends immediately, and control passes to the statement following the Loopstatement.

The Do Untilloop structure is similar to the Do Whilestructure. The difference is evident only when the condition is tested. In a Do Whileloop, the loop executes while the condition is True; in a Do Untilloop, the loop executes until the condition is True.

Do Untilalso has two syntaxes. Here's the first way:

Do [Until condition] [instructions] [Exit Do] [instructions] Loop

Here's the second way:

Do [instructions] [Exit Do] [instructions] Loop [Until condition]

The two examples that follow perform the same action as the Do Whiledate entry examples in the previous section. The difference in these two procedures is where the condition is evaluated (at the beginning or the end of the loop). Here is the first example:

Sub EnterDates3() ' Do Until, with test at beginning Dim TheDate As Date TheDate = DateSerial(Year(Date), Month(Date), 1) Do Until Month(TheDate) <> Month(Date) ActiveCell = TheDate TheDate = TheDate + 1 ActiveCell.Offset(1, 0).Activate Loop End Sub

Here is the second example:

Sub EnterDates4() ' Do Until, with test at end Dim TheDate As Date TheDate = DateSerial(Year(Date), Month(Date), 1) Do ActiveCell = TheDate TheDate = TheDate + 1s ActiveCell.Offset(1, 0).Activate Loop Until Month(TheDate) <> Month(Date) End Sub

The following example was originally presented for the Do Whileloop but has been rewritten to use a Do Untilloop. The only difference is the line with the Dostatement. This example makes the code a bit clearer because it avoids the negative required in the Do Whileexample.

Sub DoUntilDemo1() Dim LineCt As Long Dim LineOfText As String Open "c:\data\textfile.txt" For Input As #1 LineCt = 0 Do Until EOF(1) Line Input #1, LineOfText Range("A1").Offset(LineCt, 0) = UCase(LineOfText) LineCt = LineCt + 1 Loop Close #1 End Sub

VBA supports yet another type of loop, While Wend. This looping structure is included primarily for compatibility purposes. Here's how the date entry procedure looks when it's coded to use a While Wendloop:

Sub EnterDates5() Dim TheDate As Date TheDate = DateSerial(Year(Date), Month(Date), 1) While Month(TheDate) = Month(Date) ActiveCell = TheDate TheDate = TheDate + 1 ActiveCell.Offset(1, 0).Activate Wend End Sub

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