Zen Cart Modification

We need to modify the Zen Cart Quantity feature at the order submit to be changed to some word, say coverage, and to be measured with SQFT (square feet). So a cusomer would enter into the quantity box on the product page the number of sqft they have, my products come in a wide variety of quantities. As a example if a product comes in 100 sqft rolls and a customer adds 125 sqft, then the site would make the quantity 200 sqft and charge accordingly. I would also like the site to show the number of boxes/rolls that they are getting. Example of this working: [login to view URL] Only that it has to work on Zen Cart... That's your job. ## Deliverables * * *This broadcast message was sent to all bidders on Friday Oct 8, 2010 5:32:14 AM: Here is how it works. I have many products that are say, floor covering of a kind. They come in boxes that are different sizes, 100sqft, 50sqft, 90sqft. A customer can see the product, the price of the product is per box. So when the customer writes in the SQFT box (modified quantity box), say 100 sqft, if the product comes in a box of 100sqft it will add 1 box to his cart, if the product comes in a box of 90sqft, it will add 2 boxes for him. It needs to be shown to the customer how many boxes he gets.