I am not sure what function I need to use, but what I am looking for is
this.... I have a spreadsheet that lists all of my tasks. As soon as a task
is complete, I want to be able to click in the next column, same row, and
have an X populated in that field. I don't want to have to type the X. As
soon as I click the cell with the mouse I want the X to appear, and if I
click the same cell again, I want the X to be removed. Is there an easy way
to set this up? I was looking to see if there was any type of toggle button
feature that would do this and was unsuccessful.

Thanks!