Fixing the Credit Limit for customers

Hi Experts,

My client wants the system to automatically fill the credit limit  of say $0 for a customer having Incoterms as 004.

They want this to happen for each and every customer who is having incoterms as 004.

Manually Maintaining in FD33 is not agreed by them.

Please let me know if there is any standard settings that i can do to have this or do we require any Enhamcement.

Below is the screen shot of requirement.

Thanks in advance!!!!

Alam