I have a small problem of subtracting a float value from a long.

When I run the program because cust bal is a float and credit limit is a long when I come to subtract one from the other it isn't working because cust bal is not bigger than credit limit
ie.
first record:-
-2407.629 - cust.cust_bal
538969064 - cust.credit_limit
second record:-
99173.45 - cust.cust_bal
538978064 - cust.credit_limit

I have to process the record if the balance exceeds the limit etc...

Can anyone see my problem?
Thanks.