Hi Zhang,

This funtionality is not built-in to any Communications manager version at this time but is available in the latest CME release 4.3/7.0 so I wouldn't be surprised to see it in the soon to be released CCM 7.0 (Q3 2008)

There have been some threads related to this question with a workaround resolution provided by NetPro Aaron;

From Aaron;

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1dde2846/1#selected_message

Extension Mobility Enhancement Cisco Unified CME 7.0/4.3

Adds support for the following:

•Automatic Logout, including:

-Configurable time-of-day timers for automatically logging out all Extension Mobility users.

-Configurable idle-duration timer for logging out an individual user from an idle Extension Mobility phone.

•***Automatic Clear Call History when a user logs out from Extension Mobility.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/admin/configuration/guide/cmeroad.html

Hope this helps!

Rob