Help creating a base calculator

Hi everyone,

There may be a thread regarding this already and I have tried searching the web for about 2 hours looking for an answer with no joy.

I'm trying to make a base calculator based on binary, decimal and hex so that what ever number (or letter) I enter gets automatically calculated to the other the other 2 bases.
I'm doing an access course and I've been told to create a calculator to help me calculate from every possible way. I have found a some web based ones and even found an excel based one, but I want to create one myself so that I can understand excel a bit better.

Any help would save my laptop and would be greatly appreciated too.

Kungfool

P.S I'm looking to add a button to calculate but have no idea how to write a macro yet, but would this have any impact on the formulas in the cell?