Check this out and see if it helps:

http://www.empirisoft.com/support/showthread.php?t=2400

Also, try running a forum search on "dot probe" or even just "probe"--you ought to get a number of hits that could be useful. MediaLab is also set up do probe tasks, e.g., see:

http://www.empirisoft.com/support/showthread.php?t=375