Find all active clients on Visual Basic

I would like to write a program on vb for windows 2003 platform that can shutdown/Restart/Log off all active clients with a message of client desktop.
We can do it manually by calling shutdown.exe on windows. But we can't able to find active(working) client computers.
Can I do this on VB?

Working clients on what? A specific application? A network?

Active client computer = workstation that is turned on. ;)

My code here will do it for you.

http://www.vbforums.com/showpost.php...90&postcount=6