I would like info on how to create a formula where you can use a range of
letters to indicate varying values that Excel will recognise. These values
have to be written in one cell so that Excel can determine the value.
For example, A=12, B=10, C=7.5.

So that all I have to do is Put A, B, or C in the cell and Excell will
convert it to the correct value.

I hope that I have made what I wish to do clear enough, and I hope that
someone can help me.

Thanks in anticipation