I have to port excel file which business guys are using to calculate final price to C# so I can later use this algorithm in Asp.Net application. This is something I will be
I've never used it, but you might want to look at this:
http://www.calc4web.com/
It seems to do what you want, only with C++ instead of C#, but the point is that you get some code you can then compile and use (or translate if you really need it to be C#).
In the answers to this question:
Understanding / Modeling formulas from Excel
Joe Erickson gave a link to his product, Spreadsheet Gear, but I've never used that either.