PO partner check/validation

Hi GURUS,

Is there any user-exits or Badi's to help checking vendor partners when creating or changing a PO?

Right now an OA partner or PI partner from different main vendor VN can be assgined to a PO VN. For example, VN1 has OA1 and PI1 and VN2 has OA2 and PI2. When using VN1 to create a PO, we can assgin OA2 or PI2 to the PO, which is not allowed somehow because there is no relationship between VN1 and OA2 or PI2.

How to prevent this from happening? OSS notes maybe?

Thanks

JM