Google Analytics has an Event Tracking system that, I believe, applies to your needs. The details are here:
link
You add a line at the point you want to measure by creating an event (for example, a click on a top menu item).
If you use ga.js, it looks like this:
_gaq.push(['_trackEvent', 'clique-no-menu', 'menu-superior', 'resumo']);
If you use the new analytics.js, it looks like this:
ga('send', 'event', 'button', 'click', 'menu-superior', 'resumo');
Then just go to the Event Tracking portion of Google Analytics and set up your review.
Note: If you are open to other options, I recommend the Mixpanel , which was done just for this. The idea is the same as the Google Analytics Event Tracker, but in particular, I find it much simpler and more intuitive.