Transfer SC and add vendor partners in PO

Hi

I have a problem regarding partner determination on PO header

We have maintained the partner schema and this is linked to the vendor type. When we create a vendor the partner schema is selected and it is possible to maintain a different different payee and/or different ordering address.

A partner schema is created for and linked to the SRM PO type

In SRM we creates a SC and when it is transfered to backend PO I want the above partner roles from the vendor added to the PO header.

Do anyone know what to do?