>It's Larry Miller's sugestion not mine
Sorry Sergey, and Larry! (it's still a cool solution)
>
>Sergey, I've normally done the same as you: Converting the string to a val and back to a string then checking for equality (w/ original string), since isdigit only compares the leftmost char. of string.
>
>I love seeing others solutions, gets me thinking outside my box!

Another one, based on Sergey's idea in other thread:

********************************
function Zip
********************************
lparameters pcZip, pcField
**************************
If empty(pcZip) 
   return .t.
endif
local lnZipLen
lnZipLen=fsize(pcField) && len of the field

local lcMask, lcDigits
lcMask=replicate('9',lnZipLen)
lcDigits = "0123456789"
if  chrtran( pcZip, lcDigits, replicate("9", 10))<>lcMask or pcZip = "00000"
    return EvalCode(179, pcField)
endif

return .t.