Best practice to apply credit to previously paid PO

What is the proper way to handle a credit issued from a supplier for a line that was previously paid on a PO.

1. Say PO line 1 was issued for $10,000

2.  An invoice is applied to the PO line for $5000, and the amount is processed through payment

3.  The supplier issues the a credit for $1000 as the invoice in #2 should have been $4000

From what I can see, you must add a new credit line on the PO to process the credit, and also do a change order to increase the open amount on line 1 back to $6000. 

Is there anyway to apply the credit directly to line 1 instead of having to add new lines to the order?