changelog.xml file is not updating properly

Example Last revision no in svn:68000 Current Revision no:68002

Step:1 Doing a fresh checkout from SVN with a revision no. eg.62000 ....Doing Perferctly

Step:2 Updating as much as to the fresh check out with next revision no eg.62002 .This also working fine those files are added or modified with revision no 62001 and 62002 updating with new timestamp at workspace.

The issue is that in file changelog.xml those added or modified files are not reflecting.Need to know how to get update the changelog.xml every time when i will repeat with same revision no for fresh checkout and next update as much as again and again.