I found the answer to my question at http://www.stardeveloper.com/articles/display.html?article=2001112001&page=1
so I thought I would share this information. Using this approach you can create a class that implements HttpSessionListener. Then track new and destroyed sessions using the call back methods 'sessionCreated' and 'sessionDestroyed'. This class must be identifed in the web.xml file using the 'listener' tag.