Execute the Event Tracking method when you’re saving your data in back end. The other option is, execute the event in form submitting point. You can easily do this with Jquery.
Use the link below to get the selected check box value, using jquery
http://api.jquery.com/checked-selector/
once you get the selected value, pass it to the Event Tracking method.
Ex: _gaq.push(['_trackEvent', 'Theme', 'CheckBoxValue','other_Info']);