What I want to solve is the end price of a product minus a variant I think. Here is an example of what I want it to do. I have a product that is $9 an inch and the smallest you can get is 21 inches long so to start I have 9*21=$189. Now if I have a product that is 37 inches I have $9*37in=$333 and then I need to subtract the starting cost of $189 to get the variant of $144 between 21inches and 37 inches and so on up to $9*200in = $1,800 - $189 or(9*21)=$1,611.