Nor did I given that you didn't provide any kind of context for the
abbreviation, but, with a bit of Googling on TVM, and the fact that you mention
formulas within an Excel environment, I am guessing that you are referring to
the 'Time Value of Money'. Assuming that to be the case, then there are a
myriad of sites out there that will give you an overview of this kind of stuff,
eg:-
http://www.teachmefinance.com/