Should be easy to do if you split the finite string into characters
Char1: Mid(Yourfield,1,1)
Char2: Mid(YourField,2,1)
Etc... then for each column simply put a where clause
Char1 NOT between "0" and "9"
or
Char2 NOT Between "A" and "Z"
etc etc...
dont make it harder than it is. While regexp...