Not fool proof, and I wouldn't do it, but what about a script called cd in the users home directory (make sure home dir is in users path )
vi cd
/usr/bin/cd "$@"
case $(whoami) in
username) cd $HOME
;;
esac
then chmod 555 cd
also see
man chroot
Mike
"Whenever I dwell for any length of time on my own shortcomings, they gradually begin to seem mild, harmless, rather engaging little things, not at all like the staring defects in other people's characters."