MSChapV2 change-password packet request

[Serate]

Hi!
I am working around a CISCO ACS server to authorize users access in a 
web application. All is done and working but i would like now to support 
the password expiry procedure trought the MSChapV2 protocol.
I edit a user on the server with the password expiration and when i 
connect with his credentials i receive the correct message from server: 
a AccessReject packet with in MS CHAP ERROR the string with the code 648 
(Password expiry).
I studied the RF2759 and it said that the change-password packet (id =7) 
should now be sent to change the old password with a new one.

I am using jradius to communicate with the server but nothing i found on 
internet about it and the use of the change-password packet (examples or 
something other).

Actually i found some sources (es. 
http://www.opensource.apple.com/source/eap8021x/eap8021x-100/EAP8021X.fproj/mschap.c) 
and i am tring to implement them converting the logic from C to java but 
it is going to be a very hard work.

Does somebody know something (examples, sources, libraries) about the 
change-password packet sending?

Thanks, bye
Emanuel