It seems crazy to me that you would not protect the salesman.  It is the salesmen that brought in the account he should be compensated always. This is called an exclusive contract.  Why to you object to paying 5% to a salesman when his account is bringing in more business?

This is business that you did not have, business you were not able to get on your own.

Perhaps you have not been in our industry that l

ong, we have always used independent reps and as far as compensation goes 5% is a little cheap, 10% is our rate.