vba while. code example

Example 1: vba while loop

i = 0
While i < 100
    'Code here is executed 100 times.
    i = i + 1 
Wend

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'Notes: The While loop is terminated with the 'Wend' keyword.
'
'       The While loop must include a Boolean expression directly after
'       the 'While' keyword and the loop will execute for as long as the 
'       Boolean expression evaluates to True. This expression should be
'       based on something that has the POTENTIAL TO CHANGE on each cycle
'       through the loop. For example, 'i' in the above code.
'  
'	    The While expression is evaluated at the beginning EACH cycle through 
'       the loop. The expression DOES NOT NEED to be NUMERIC; but it must 
'       evaluate to True or False. The While loop will be skipped entirely if 
'       the expression evaluates to False before the loop begins.
  
'       The following code demonstrates how the above While loop
'       functions (without actually using the 'While' and 'When' keywords):

i = 0
LoopStart:
    If (i < 100) = False Then GoTo LoopEnd
        'Code here is executed 100 times.
        i = i + 1
    GoTo LoopStart
LoopEnd:  

'      This is for demonstration purposes only. Although these two loops are
'      equivalent, using the 'GoTo' statement should be avoided. The While loop
'      accomplishes the exact same task, but cleanly, without the 
'      line labels and without the 'GoTo' statements.
'
'Note: VBA does not include an 'Exit While' statement to terminate the loop
'      early. VBA does include the 'Exit Do' statement for the Do loop and 
'      also the 'Exit For' statement for the For loop. But it is possible
'      to exit the While loop early with a 'GoTo' statement, but again, the 
'      'GoTo' statement should be avoided. It's also possible to exit
'      the While loop with the 'Exit Sub' and 'Exit Function' statements.
'      But of course, these last two statements will not only exit the
'      While loop, they will also immediately exit the current procedure.
'    
'Note: From an efficiency standpoint, the For loop may be a better choice
'      than the While loop because the For loop's range is calculated only
'      once, before the For loop starts. By contrast, the While loop's
'      expression is evaluated before each and every cycle of the loop.
'
'
'

Example 2: vba do while

' OPTION 1
i =0
Do While i < 3 'Check Condition at the START of the loop
  ' Do something
  i = i + 1
Loop 

'OPTION 2
i =0
Do
  ' Do something
  i = i + 1
Loop While i < 3 'Check Condition at the END of the loop