Tracking User's Location at a certain point
You can append a different query string to each click, which will allow you to track each one individually. Lets say your "Start Timer" is at mysite.com/start_timer (using ajax). You can create several url's with a query string that lead to the buttons. Ex:

mysite.com/start_timer (using Ajax)

mysite.com/end_timer (using Ajax)

Then you can use Google Analitics Event Tracking Module which will do your work for tracking easily.

Enjoy !