magento price ajuster extension

I am developing a site for window blinds and curtains the problem is that every 5cm increase in width or drop the price needs to ajust higher as the size of the blind/window increases. Not only that there is 3 different price structures for 4 different types of blinds. Also the selector tool must be compaitable for mm cm and inches. I have the pricing tables already in CSV. I have seen sites with this tool so there may already be a plugin/extension available or someone may have one for a different product range that can be be modified. Hope someone can help. please see a link of a working site to have an idea of what i need [login to view URL] notice as for example you put in 1600mm width by 1200mm drop price increases from £23 to £37 looking forward to hearing from you