Hi,
You'll need to vi .profile of that user. Do this:
# Limit number of logins allowed
Times_allowed=2
Time_in=` who | grep $LOGNAME | wc -l `
if [ $Time_in -gt "$Times_allowed" ]
then
echo "$LOGNAME is already logged in $Times_allowed times!"
sleep 3
exit
exec /bin/login
fi
Then you'll have to chmod 444 and chown root .profile.
Hope this will help.
cheers,
Mok