Receipt Aware Criteria

We have the system setup so that we can create vouchers on POs and they match once PO is received. Where do we set up this "Receipt Aware" criteria? I want to create r600 error- (The Matching process found receipts for this purchase order that were available for matching (for example not matched, not on hold, and not cancelled) but could not make an association to the voucher line using any of the receipt aware criteria.) We want to create this exception but not sure what triggers the it.