TMOUT question

[mvjta at mvgpn.att.com]

This may be a future FAQ entry but here it goes again.  In my .profile
I have put in TMOUT=300.  This works fine in my home directory but if
I cd or go into another process (one most would know is rn) and leave
my terminal on it doesn't time out.  I've seen this question phrased in
different ways by system administrators wishing to track idle terminals
but I am just looking to find out if there is a simple way to have my
TMOUT recognize any idle process.  I have a feeling that it isn't as
trivial as it sounds so even a simple "no you can't" would satisfy my
curiosity.  
   
I'm not a programmer and my knowledge of UNIX commands revolves around
modifying my .profile so a complicated programming solution wouldn't do
me much good.  It's just that our supervisors frown upon leaving our
terminals unattended.  We use UNIX System V release 3.1.5.  Thank you.
Tom Abar