Hi
Nothing builtin that can help you here I'm afraid.
The UserLock product in the link below is an option
http://www.softwareshelf.com/products/display.asp?p=42
Microsoft's solution:
You could install the CCONNECT Microsoft Resource Kit utility onto every
computer, it is in the Win2k Server Resource Kit, Supplement 1 (pay ware, and
you will need a SQL server database as well).
More about CCONNECT here:
http://groups.google.com/[email protected]
Here is a third option you might get to work:
Tip 296 at
http://www.jsiinc.com/
and
0296 » A better way to prevent a user from logging on more than once.
http://www.jsiinc.com/SUBA/tip0200/rh0296.htm