BDC for Rebates

Hello,

Can any1 please guide me on how to implementing Rebates as per following:

Rebates to be applicable on a sales office

It should apply to invoices created for that sales office

Settlment should be as per indivisual customer.

If there is new customer then Rebates should be apllicable to that customer also.

Should be able to change the value in future.

And can we upload these using BDC.

Thanks in advance!!!!