Force userers in a member group to change password

[higherauthority]

I just upgraded from 1.07 to 1.1RC2  I see there is an option to have high strength password policies.  This is great. But all the low strength password are in effect until the users decide to change them.

Is there any way that it can be made to force certain member groups like global admins and such (people with admin type rights) or even all members to change their password other then sending pm's and hoping that they do it. 

mabye even a possibility to force a password change after a setable time limit   ie...  1 month 2 months year etc.....

I think it would enhance security. Just not to sure on how difficult it would be