In MS Access, how do you convert a CHAR to Decimal so i can compare in the Where?

For some dumb reason, a currency amount is recorded as a char(10) and i must compare to find if the amount paid is less than the amount due. I have been using CAST(es.AmtDue AS Decimal) > CAST(es.AmtPaid AS Decimal) in my WHERE, but is throwing an error. My syntax may be incorrect or I may just be on the wrong track, any ideas?