I remember having to do this for csh, but it should be a similar solution...as I recall you have to alias the cd command to update the prompt. So something like
"'alias cd '\!* ; set prompt="`hostname`:$cwd % "'
It's a kludge, but it works. This site might also help: http://wwwinfo.cern.ch/hepix/wg/scri...ells/user.html