User Exit or BAdI for VA01 partners tab

After creating a Grant from the GMGRANT Tcode, after pressing on "Change Status", a Sales Order is automatically created. Currently in the Partner Function tab, all partner types are filled with the "Sold-to-party" partner. I need that 'Bill to party' and 'Payer' will be taken from an 'Sponsor'. I tried to find a BAdI or an User Exit without success. Any suggestions?