Programmer to build a web-based calculator. NOTE! I have no clue what language it needs to be built in!

Programmer to build a web-based calculator. NOTE! I have no clue what language it needs to be built in! I sell on eBay, Amazon, and other venues. I need a web-based profit margin calculator to be built for me. I have the beginnings of the user-side, but the builder & I parted ways before he got very far (and I have no clue what programming language he was using). The basis of the calculation is Selling price - Cost - Shipping - Fees = Projected Profit Margin. The Lister/User enters the Sales price (will vary for each site), the Cost, the weight of the item, and if it can be shipped in a Flat Rate postal box. The program calculates the shipping based on the information given and other factors you will program in. It also calculates the various fees for each site and fulfillment method applicable. Profit Margin is then displayed for each venue/fulfillment option so the lister can see which places it will be profitable to list an item, if at all. If you are interested, I have attached project details including a Programmer's Synopsis and a link to the partially built site so you can give me an accurate bid and timeframe. This is a one-time project, but could develop into more than that. For a variety of reasons, Priority will be given to Filipino workers.