Click to insert character

[bfields]

I have two cells, I would like to be able to click on one and have a predetermined character insterted into that cell. If I click the other cell I would like the character to be turned off from cell one and inserted into cell two. I am trying to make a check list that shows if a certain task has been completed or is in progress, so I would like to be able to click the in progress cell, have a check mark apprear and then when the task is completed to click the completed cell and have the check move from in progress to completed. Please see attached spreadsheet for example.
Thanks-