def variable i as int no-undo.
def variable s as char no-undo.

s = "sdghwsthsw5yasrygw6u".

do i = 1 to length(s):
 if lookup(substring(s,i,1),"0,1,2,3,4,5,6,7,8,9") <> 0 
 then message "Captain we have found a digit" view-as alert-box. 
end.

I use the INT function with NO-ERROR and check ERROR-STATUS:ERROR