I am creating a spreadsheet that will allow me to keep track of a football
game's statistics by entering the result as each play occurs. Generally, no
problem. However, plays randomly result in first downs, and when that
happens, I would like to "mark" the cell in some way. Then I will create a
cell that simply counts how many of those cells there are, which will give me
the total number of first downs.

My question is, in what way can I "mark" the cell? Whatever way I do it, the
worksheet must still be able to access and use the number entered in that
cell.