Automatically allocate returns to the vendor

Hi , I'm using Oracle EBS ERP R12.2.11 version.

Currently, we have two Operating Units, A and B. 

B serves as a supplier to A, and A issues purchase orders (PO) to B. Simultaneously, B creates a sales order (SO) with A as the customer. 

Now, I am seeking a way for A to automatically process a return to the vendor when B creates an SO Return, and B has already initiated the Return Merchandise Authorization (RMA) receipt.

Note: The price of the SO Return may not perfectly match the PO, as the orders may involve a many-to-many relationship.

May I ask for any polite suggestions?