Can we link AP invoice/Payment to AR Transaction

Hi,

We are on Federal Financials R12.1.3.  I have the following scenario:

Example: An payment is made to Vendor(Joe) for $5,000, and it is later determined that it only should have been $4,000. NSF creates a receivable with customer (Joe) to pay back the $1,000.

 

1.       Is there a way to link the AR Invoice to an existing AP Invoice/Payment in EBS?

2.       Once the AR cash receipt is recorded, is there a way to make those funds available again on the obligation for future spending.

I am looking for the best practice inOracle EBS to address this requirement.  PO is not closed but we have a need to reduce obligation on the PO.