Invoice recipient partner function

Hi,

Our users should be able to select an invoice recipient address on the shopping cart line from the list of available addresses. The selected address should flow onto corresponding PO line.

Can I use the standard partner function 00000028 Invoice recipient? How can I make it visible on the Shopping cart line item screen in the Partner section?

I tried to create a custom schema with function 00000028 and use my schema as partner determination proc for BUS2121 (under define transaction types). This configuration gives me an error “Business partner is not defined”. What am I doing wrong?

Thank you in advance