product quantity update script

OK so this will be for an ecommerce site. Zen Cart 1.2.5 I have already had most the script done but need it finished. So far it works like this. You are looking at a product that has several color and size attributes. With a starting price of 10.00 for the product but if you want to make it larger you select a attribute that makes it larger it show an increase in the price. However the catch is if you want to have 2 items it does not show the updates price for 2 items only for one so I need that part of the script written or fixed. I suspect it is less then an hours work I have some of the extra code to make this work but do not know how to apply it.