Can one create a "Change password on first login"?

[Joao Clemente <jpcl@rnl.ist.utl.pt>]

Hi.
Does anyone knows of a method to implement a "force user to change 
password on 1rst login" feature, as we can have in win (2k,at least)?

The goal is to create a username/pass for a user in a way that, when it 
first sits on the machine, it if forced to change the passwd.
A secondary goal was to have a way to, at a certain point in time, 
activate that "mode" for all users in the system, so that everyone would 
be forced to change it's password on next login.

Am already thinking of a way to do this looping "userpasswd" while 
password is not changed, but maybe there is a way to do it without tricks...

Thanks
Joao Clemente