Wanrong Lin <wanrong.lin@gmail.com> writes:

> I would like to record down the time stamp when a TODO item changed its
> state into some specific states (like "DELEGATED"), but I don't want to
> be prompt with a window for notes. 

I like the idea.

Here is a patch against latest org.el from git that implements something
that might suits your needs.

If you add "%!" to one of the heading in `org-log-note-headings' then
Org doesn't pop up a new buffer, the log is filled automatically.

(setq org-log-note-headings 
      '((done . "CLOSING NOTE %t") 
        (state . "State %-12s %t%!") 
        (clock-out . ""))))

Carsten, if you like it, I push it and update the manual accordingly.