Custom Calculations

I am creating a website for someone who makes made to measure curtains. I need to be able to have a width and a drop entered by the user, the price needs to be calculated based on these two options from a table like below along with a few other options - type of headding etc. 10 20 30 40 1 53 59 57 69 2 57 62 63 75 3 61 68 67 80 4 65 75 78 83 The site is to be created in opencart - I need some one to customise the options and the shopping cart to calculate the price based on the amounts entered by the user? Thanks Deb