Calculator Box

In need of a calculator for customers. Basic multiplication. The product is a loose fill substance. The customer needs to be able to select the product (from a dropdown) enter the length/width OR square feet of their surface, select the inches of product to be applied (between 1 and 6 inches from a dropdown), and select the units of measure (bags or bulk from a dropdown). The calculation should calculate the amount of material needed and the cost. The cost will vary depending on the color chosen and the units of measure, even when square feet is the same. For a specific example, I will PMB competitors site. Some rounding will need to be used. We need an infobox of sorts. To be placed in existing php and html files of an oscommerce site. Let me know if you have questions. Winning bidder to provide any and all files pertinent to installation, file placement, and modification of the code. An escrow payment will be provided until successful completion of project.