Customer Credit Limit - How to block if not limit is set?

Hi,

we are using static credit check for our sales orders. Credit
limit is maintained at the payer level.

Is there a way to block an order in case no credit limit is
maintained for the associated payer?

Customers credit data(fd32) is maintained seperated from the
remaining Customer master data (XD02). Is ther a way to make the FD32 data
mandatory as soon as a customer is a payer.

Thanks