extending the product item page variable width/height search

Hi

I am building a website for a customer, in a nut shell, on the indervidual product page, they need their users to be able to type in heigh and width, which will automatically calculate which product will be needed and then it will automatically add the product to the shopping cart. so for example, if i wanted to buy a window which had a product specification of 500 x 1000 but the user typed in the width box: 400 and height box: 900. It will then popup the product that they need to buy closest to the users specifications (without going over) then add that product to the shopping cart. Can this be done in php open cart?