in reply to Kill a script at a certain time

If your script is named, you can put something like the following in your crontab:
00 16 * * * kill `ps -auxww | grep | grep -v grep | perl -an +e 'print "$F[1] "'`
(I couldn't help but slip some Perl in there ;-)

Obviously, you may need to customize it to whatever environment you're using (e.g., `ps -ef` if you are using HP-UX etc.) and whatever other contingencies you may anticipate (e.g., you'll note that in its current incarnation, if file appears in the argument list of the call to your editor, your editor will be killed as well every afternoon at 4:00pm). But that's the basic idea.

Hope this helps!