KAE1994 -
Please don't post the same question more than once, you will find most
people here read every thread and it gets annoying to read exact duplicates.

With that said, and reading your previous post, this sounds like a math or
finance question.  This is an Excel help chat so if you don't have a question
specific to Excel then please don't post.

Your best bet would be to search through the templates offered on office
online, they may have something to deal with what you are after:

http://office.microsoft.com/en-us/templates/default.aspx?Application=XL&Ver=11

As far as any kind of exact finance formula, ask your prof.