Calling an Oracle API to get price

I would like to replace the current price lookup within cs-cart with a call to an API inside an Oracle database. I can write the Oracle API, but do not know where in cs-cart to replace the code.

For example, I have negotiaed a price list with several clients and have that information maintained in an in Oracle database. As you shop, display, and select products I would show you your contracted price based on your identity.