can't, unless you can run a process on your machine as that user. The only way to do that is with the MSTC way, or the WMI way. still can't remember the WMI way, but here is a work around.
run compmgmt.msc.
when the console opens, right click computer management (Local) and select connect to another computer. At the prompt, type in the computer name or IP that you want to connect to. Then it should prompt you for login credentials, since you don't have them. Once you are connected, right click Computer management again, and select properties. Then wait for it to load. Once loaded, go to the advanced tab, click settings under startup and recovery, then shutdown (near the bottom). Choose log off current user and always, then click ok. That will log them off.
good luck