I have not tried this, but, how about doing something like this...

Copy the LOGOFF.EXE file to all of the systems.
Create an AT schedule on all of these systems that runs say once every couple of hours. Then have it look for a zero byte size flag file. If not found have the AT service execute the LOGOFF.EXE file. In the Run or Startup group have the system create this zero byte flag file so that the system will not keep logging off accidentally. Then if or when you want to log off a system you can remotely delete this flag file.

Or possibly something like this:

at \\remotecomputer 13:00 cmd "/c logoff.exe"

I also found this resource on the WEB that might work or be helpful. He has a remote logoff utility in pre-beta. http://wwwthep.physik.uni-mainz.de/~frink/nt.html

Please post and let us know if any of these solutions/suggestions work out for you.

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NTDOC...
The dark side is quicker, easier, more seductive.
If you choose the quick and easy path, you will become an agent of evil.