can sieve script flag the whole thread?

[Zhang Weiwu]

Hello.

I read the RFCs and documents I can find on the internet, it seems it's 
not possible for sieve to flag a thread.

I need such an action that not only setflag the current email, but also 
any other emails in the same thread in the  folder. This is useful to 
organize workflow in our business, each workflow is a discussion thread 
and if someone send an email to this thread with subject "Done",  the 
whole thread should be flagged or moved to another folder.

Being able to setflag (or move messages) for a whole thread of 
discussion is vital to use sieve to help us organize email, otherwise 
we probably wouldn't put as much information in email and try develop a 
web application on our own. Can this be done? Help really appreciated.

Best regards
Zhang Weiwu