Customizable Price Calculator

Our business is an ecommerce. We operate on our own website as well as mainstream marketplaces in Brazil. We focus on backpacks, purses and travel accessories. Most of the time, we sell the same product at more than one or two marketplaces simultaneously. However, the cost structures change substantially between marketplaces, with different selling and transportation fees, even though it is the same product with the same product-cost. Therefore, considering one specific product and its specific profit margin target, we'd like to be able to "equalize" the price between different marketplaces. We'd like a calculator app for that! The following assumpations should apply to this project: I) to be able to freely distribute it to any of our employees (< 10 individuals); be it a PC app or a web-based application, we want to be able to deploy it in the firm II) to be freely and quickly updatable: we want to be able to dynamically adjust our price to different market conditions; whether daily or monthly, we want it to be updatable at any time with different pricing parameters III) to be customizable: not only parameter values move in time, their structure also may change; for example: one specific marketplace used to charge us a % fee on every transaction; later, they started charging a $ fee on top of the % fee for low-price transactions; and so on. We'd like the calculator to be customizable regarding both parameters and marketplace structures We are a small firm. We aren't able to pay much for it, but this experience would contribute a lot for volunteers, as the developed solution would fit the needs for many ecommerce SMEs like ours!