Custom Shopping Cart Setup

Hello,
I am setting up an online store for custom computer building. I would like to create a page that allows users to use something such as Jazzy Forms to customize the options they want in their computers and in turn calculate the price based on the options they select. I then want this price to be able to be plugged into a PayPal buy now button or something similar so that they can easily set up their computer and buy right there. Any suggestions?