No problem I probably didnt explain it as clear as I should of...
High level process is:
1) MRP generates a PR on receiving plant, and transfer request on supplying plant
2) Supplying plant creates a delivery without reference (VL01NO)
3) Upon PGI of that delivery, the Z_MB_DOCUMENT_BADI is called which takes information from the delivery, along with a custom table which links the custom and vendor #s together ( similar to the standard STO configuration) , calls the PO_BAPI_CREATE1, and creates a PO in the receiving plant. It creates a ZNB or ZUB based on the delivery type from the delivery. Material is also issued out of the supply plant at this point
4) From there standard GR processing happens to receiving in material to receiving plant
This works great if its a inter company scenerio, but intra company it causes a lot of manual accounting fixes becasue of the GR and IR postings which generate.
My solution was to change it to act more like a UB (but without a need for delivery) but as you can see a GR posting still creates a FI document on the price of the material (not the PO - which is zero)
This is why I was starting to think of looking at a BADI or exit at time of GR which would stop the GR posting from according but still receiving in material ( Like a standard UB).
Hopefully that answers your question and gives more clarity... Its a tough one since its a custom process (in which I did not design but inherited) which hopefully we can change at some point, but for now that is not an option so I am looking else where.