I need to create a "program" with an Excel document that allows me to click a
button like "start adding" and then I can click on random cells (well, they
wouldn't actually be random, but not in any series of columns or rows), and
the contained values to be copied to successive cells in an empty column on
the side, that I can then have a Sum setup up on.

Basically, I have different pieces of equipment listed in an Excel
spreadsheet, along with various options. (Several hundred) I want to be able
to select which ones (even just by clicking on the price/value), and
automatically add them together - currently this is done on paper. (The costs
of the various options, etc. are scattered about, and aren't all in a
particular row or column.)

Once I'm done calculating it, probably I'd need to have a "Stop adding"
button that I could press and then it would stop calculating the value.

Preferably it only copies the actual number in the cells to the new
location, as many of the cells are themselves calculated by formulas.

Can anyone think of a way of doing this? I've been looking around for a way
to do this, but I haven't found anything that will do it yet.

Thanks in advance to anyone who solves this problem!