I want to show the difference between two values both in numerical terms and
percentage terms in a single cell preferably. I know I can create two
separate columns but that will lead to a monster sheet that I am trying to
avoid.

Is there a function in Excel where you can add two (or more) values to the
same cell and when a person scrolls over the cell - he/she has the option to
choose which value to view - or something like that...