Add a field to Document Output POWL?

Hello all,

I want to add a field "purchasing group" in POWL for the type Document Output. I have read the document http://scn.sap.com/docs/DOC-25692. It's for SC. I tought this could be useful. But it just doesn't work. The feeder type of Document Output POWL is SAPSRM_FEEDER_DOUT. Someone can help me? Thanks a lot.

Best regards,

Ruijia