Maybe
set filter to ! (isnull(ZipCode) or transform(val(ZipCode), '@L 99999') == ZipCode)
>the following code:
>
>set filter to ! transform(val(ZipCode)) == ZipCode
>
>reveals blanks and zipcodes beginning with 0 as well as those containing alpha characters.
"The five senses obstruct or deform the apprehension of reality."
Jorge L. Borges?
"Premature optimization is the root of all evil in programming."
Donald Knuth, repeating C. A. R. Hoare
"To die for a religion is easier than to live it absolutely"
Jorge L. Borges
