Problem with a GUICtrlCreateUpdown in Windows 2000

I am using an updown to walk through an array.  When I test it on my 
home computer with XP its works fine.  When I use it at work with 2000 
it does not work.  The message box will not even pop up when I click on 
the up down buttons.  Like in the example below.  The numbers will 
increment in the input box but it will not trigger the code that I have 
to walk through the array in a different input box. 

Case $msg = $updownControl
   MsgBox(0, "test", "test updown")

Is some kind of as nofity option that I am miss?