Capturing user clicks within Spry Tabbed Panels

["pixel1024"]

Hi,

 I am using the spry tabbed panels with CS3 for the first time and need to 
capture when a user clicks on a new tab. I need this to re-set a PHP variable 
when the user navigates to a new tab but cannot see any documented way of 
getting this trigger. 

 Any help would be much appreciated!