Tally Marks?? Or something EASY to use for keeping track of calls??

I am making a spread sheet for someone to keep track of all the phone calls they make in a day.
Until now he uses a peice of paper and uses tally marks. Up to 150 tally marks.

Can anyone think of an easy way for him to click something and it will keep track of how many calls its been or something silimar?

I am stumped.


Thanks!