Commission payable to a vendor on customer billing for order receipt.

I want to set up a procedure through SD billing to pay certain amount of comission to a vendor on customer ( sold to party) billing. Comission amount should be credited to vendor account automatically on billing to sold to party. I have thought of setting this procedure through Rebate processing. If this process is right please guide me how do i create the settlement credit note on Vendor account ??.. or please suggest me relevant procedure.

Thanks & Regards

Avinash