width X Height = Change the price

[2maz]

Hi,
I know many people are looking around for a solution for selling pieces of shirt or stickers by surface customisable by user like "I want 1.00 m X 2.50 of you beautifull shirt"
How to connect two fields Width  and Height  than calculate a Surface and modify the price to be in accordance with the surface.
Typicaly it's needed by any shop who sell products in m2 like shirt or stickers. So if anybody have an help. I've turn around the core hack made for VM1.1 but it's a little bit hard for me to adapt it, many bugs, the php code of VM had evolved.
Creating customs fields is not the solution, it ask to create a value for each millimeter Width and Heigth and it can concern small or big pieces of shirt with a change in percents for each new value.
I'm despited not to be a good php developper and solve it by myself. Don't you think that this kind of possibilitties to buy a piece of anything on the web is a must have in 2012 ?
Thank's