If you need to include subdirs, there is the full-featured DirPlus() UDF that Bryce wrote, otherwise you could use my lean DDir() UDF to enum dirs one level deep.
Code:

Function DDir($Start)
  ;Does not support WildCards and FileSpec must end with \ 
  Dim $TmpArray[0], $Dir, $Index, $
  $Dir = Dir($Start)
  While @Error = 0
    If $Dir <> '.' And $Dir <> '..' And GetFileAttr($Start + $Dir) & 16
      $TmpArray[$Index] = $Dir
      $Index = $Index + 1
      ReDim Preserve $TmpArray[$Index]
    EndIf
    $Dir = Dir()
  Loop
  If Ubound($TmpArray)
    ReDim Preserve $TmpArray[Ubound($TmpArray)-1]
  EndIf
  $DDir = $TmpArray
EndFunction


Either one returns an array and using a FOR loop, you can iterate through them.
Code:

For Each $Folder in DDir('C:\ParentFolder\')
  ;do stuff
Next
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