[Dovecot] Changing password for users

Hello,

I am using dovecot (2.0.9) and using virtual users using

passdb { args = /etc/dovecot/dovecotpasswd driver = passwd-file }

How can i make my virtual users change their passwords using web interface ?

My users already uses squirrelmail to access their mail. is there a program to add to squirrelmail to add this function to the clients ? or should i user different separate website for password changing ? and what program/tool can help me with this ?

Any ideas is greatly appreciated.

Mike.