I have a customer that wants to attach any documents that are on the Posting Proposal Screen to the PO Screen if there is a PO Reference on the Posting Proposal screen.

The issue I am running into is there is no match for some one the transformation methods between the two objects.  It appears I can use either the PostingProposal LU or the ManSuppInvoice for the source LU but the target LU, PurchaseOrder is missing matches for INVOICE_ID, PROPOSAL_ID and ROW_ID. 

I did see one article that added a custom field to match the transformation and I tried to add Invocie_ID to the target LU but I could not get it to show in the transformation method.

Any help would be greatly appreciated.