Restrict Related Products to particular Author (Seller) when used with UC Marketplace

I would like to restrict the selection of related products to only those of the author currently creating the product. I have this installed with Ubercart Marketplace, and I only want a given author/seller to see their own products when they choose related products int the product node creation form. Currently all products by all authors are available.

Any ideas on how this can be achieved? Thanks very much.