Dynamic $PS1 content on AIX 4.2 ?

I am trying to set a dynamic PS1 that will change its content no matter what the user does. But I am finding that the shell variables I put in it do not get refreshed.

One simple example of what I mean :
PS1="$HOSTNAME:$USER $PWD > "

if the user changes directory, the PWD variable is not updated. It still has the values set at the initial PS1 setting.

How can I have any variables in PS1 be dynamically updated on each value changes and be transparent to what the user is doing ?

This is on AIX 4.2 servers with Korn.

Check this thread

Thank you.

Seams to be working.