I am attempting to use something similar to the ISNUMERIC function to
determine the result set of an SQL Query but it tells me that the
function is unknown in Interbase. Is there a similar function to do
this? The sample code I am trying to recreate is basically like:

select ROLLID,SKLOCATION from STOKFILE where ((SKLOCATION IS NULL) OR
(SKLOCATION <> 'USFW')) AND (ISNUMERIC(SKLOCATION)<>1)
union select ROLLID,RLLOCATION from rollfile where ((RLLOCATION IS
NULL) OR (RLLOCATION <> 'USFW')) AND (ISNUMERIC(RLLOCATION)<>1) ORDER
BY 1

I need to show all rolls in non-numerical locations but LOCATION is a
String field.

Thank you for your help.