I need to be able to calculate a different price for some users based on a variable from a php script run outside of Zen Cart. Being very new to Zen Cart, I don't see how to inject a new price into the customer's shopping cart. What is the name of the variable in the shopping cart, and on what page would that be found? I don't want to change the actual price of the item in the database, just the price one time for a particular customer. They'll get individual discounts in particular situations based on purchase made on a sister site...