How to direct back to logon screen after VD log off on Ubuntu 10.0.4

I want a similar experinece we have with Thin Shell on Windows for our Linux Ubutnu 10.0.4 machines. They are set up to automaticlly connect to the specific virtual desktop, however when a user logs off it takes them back to the Ubuntu desktop. How can I instead log them off Ubuntu as well so it shows the log on screen?