RTRIM() I would think, Duncan. ALLTRIM() would mask whether or not the user put a blank first and I don't think you want to assume that blanks are padded with 0, that's not how I read Chuck's problem.

What about simply lValid = INLIST(LEN(RTRIM(cVal)),2,4,6) AND LEFT(cVal,1) # " "

The InputMask takes care of the rest....
>?INLIST(LEN(lcVal), 2, 4, 6) AND PADL(INT(VAL(lcVal)), LEN(lcVal), '0') = lcVal
>
>Will, I believe, give you what you want. You may need to ALLTRIM first.
>
>Regards,
>
>Duncan