How to handle third party fee for end customer relationship?

Hello!

We have an arrangement with a distributor to ship/sell product to a 'big' company. The distributor raises a sales order with the 'big' company being the ship to and bill to. We ship product directly to the 'big' company, and the 'big' company pays us. We then need to pay the distributor a fee for the relationship. How can this be done automatically? Add a service item to the sales order which then raises a PO for the distributor in which we then process a supplier invoice?

Any insight/feedback is greatly appreciated!

Thanks.

Julie