REFERENCE1 - 6 fields with manual encumbrances

We have a number of "FINALLY CLOSED" purchase orders that have balances.  Some time ago manual encumbrances were put in to offset them.  The problem here is that the reports show both entriies because it doesn't know that the manual JE goes with the PO.  If we could populate the  REFERENCE1 through REFERENCE6 FIELDS with the types of identifiers put in those fields by Purchasing, Requisitions andi Payables.  Is there any way to access those reference fields while entereing a manual encumbrance?

Thanks,

John