SQL Developer and Mathematician to Write Algorithm to Turn Losses to Profit

Maths has never been my strong point, how I have go this far in life is beyond me! My Problem is with product pricing. The products I sell need to be sold at Retail Price [MSRP], however sometimes that just is not possible, due to online fees, delivery charges etc. I have got as far as working out my Gross Profit Margin (which might not sound like a big deal, but for a guy that is learning to code this in SQL and Failed secondary school maths with an F is a big deal!). So I need someone to write me an algorithm to turn these negative figures around to positive figures but without just writing a linear 10% increase approach. Apart from anything, that simply wouldn't work especially since some figures are -40%! I'm working with Microsoft SQL, and do have some limitations in what commands can be executed since this is a hosted system that manages my products. For example INSERT INTO cannot be used. All said, whilst I am working with SQL, I don't necessarily require a developer. If you reckon you have the Mathematical skill to coach me through, I could work with you to develop the solution. *** PHP Developer. If you are an SQL/PHP developer, there is also scope here to make this a larger project, the cloud solution I am working with has an API, so writing some kind of portal with firewall style pricing rules may also be an approach that I am open to work with. *** I have attached some examples of figures that I am working with, and can supply the MSQL I have written so far to obtain these figures... I trust you will ask more questions, frankly I am unsure what other questions to write to gain the answers! :-/ Look forward to hearing from you..