MSR - REQID in the IN_DEMAND table

MSR is created using custom AE using the modifiled version of the delivered Component Interface of Stock Request. This is followed by IN_REPLEN_AE creating replenishment request based on the "Demand". Then a PO_REQLOAD creates the REQ and eventually a PO is created.

question is how do updaet the IN_DEMAND table with the REQ_ID or how to populate say a custom table that links the MSR with the REQ_ID which is linked to the PO. Currently there is no way to know the PO# for a demand (MSR).