Credit to a customer

I have two customer that are paid by one company.  There was a credit say a $5.00  to the first company and they discounted that amount from what the second company owed. So the second company owed $200.00 and with the discount they paid $195.00.  If I enter the $195.00 payment to the second customers it will still show that they owe $5.00.  How can I take the credited amount from the first customer and apply it to the second customer in Timeslips?