OK now I've installed a little file called TV7.cmd on seven computers. It contains the two lines as suggested by aniceguy, and each command file is accessed by a shortcut that runs the command file minimized:
net stop TeamViewer7
net start TeamViewer7
This command is executed on the remote to close the session with the remote. It works fine on XP, Vista, and Win 7 remote systems, even does away with the "Sponsored session" popup that otherwise sits on the remote screen after a session is closed. Except: On Vista and some Windows 7 remote systems with UAC on, it must be run with administrative privileges, requiring extra commands to make that happen (right-click the command file or its shortcut, select "Run as administrator," click "Continue" on the permission screen.).
It's not a big problem, because if I just click on the shortcut without elevating to administrator, nothing happens and the session will not close. But it would be nicer if it just worked. Anyone know of a way to execute the NET START and NET STOP commands from a command file without going through elevation to administrator? UAC must stay on, of course.