Modify product display and product attribs

I'm not sure this is even the place to put this so I apologize in advance. Doesn't really seem to be a related category.

I want to make a mod that allows the admin to select 'commission product' or something akin to that on the insert product page in the admin form that will replace the 'add to cart' button with a 'purchase' button that links to an url that is also specified in the admin page.

The idea is that this way I can not only sell our own products using the cart, but for the case of products where we get a sales commission we'll also be able to collect on that.

Although it would be nice if something like this was already implemented, or if there was a mod out there that already did it, I can probably write this myself but I'm finding the actual page that builds the 'insert product' form so I have nothing to go on.

Any ideas where to begin?