Margin Calculator Help

Hello Everyone,

I come here in frustration and fully aware of my lack of adequate knowledge, hoping that someone out there can point me in the right direction.

I'm toying with the project of creating a margin calculator app for our company that allows our reps to see our product costs and calculate what selling price would be based on what margin they wish to sell at. The catch is that I would like for the costs to be reflective of the value associated with them from a spreadsheet (Ex: widget A= $200, widget B=$300 etc). In essence, the user could scroll down a list of selections, choose the widget they want and have the cost for that widget pop into the "cost" display. Then they would input the margin to get a final sell price. I can't find any plugins or other source codes that are similar in this function and any help would be appreciated.

Just in case any are wondering the reason we are doing this on our own (and why I got stuck with it) is because our company is only 9 people, and since I seem to be the only one capable of understanding how difficult this is, I got tasked with it.

Thanks for reading, and Happy New Year.