security for Windows logoff scripts writing to log files

[Kevin Shalla <kshalla () UIC EDU>]

I'm writing a vbscript logoff script to track time, computer, IP
address, username, and other stuff for our Windows computers.  Now
I've got it configured so that the script (on the server) is open to
everyone for reading, and the log file (again on the server) is open
to writing for everyone.  Before I put this into production, I would
like to set it so that users can only update the log file while
running the logoff script, and then can only append records at the
end.  Is there a way to set this up?