Write Cell Equations based on Userform selection

Hi,
I would like to be able to select one group of cells (Group 1) and a second Group of Cells (Cell 2) and then have Visual Basic automatically write the cell equation and write a corresponding string above it.

The cells may not be a continuous range. I've attached a sample excel file in which this operation has "already been done"

The reason I'm asking such a broad question is that I'm not even sure if it's possible. I thought one of you might know.

Thanks in advance.