Is there a way to configure the dialplan so that the FS could terminate the conference session upon certain condition?

The scenario is:

1. User A dials a number
2. FS starts a conference session by ringing User B and User C ( and User D or any number of other Users )
3. User B joins the conference ( along with other invited Users )
4. After talking a while, User B leaves the conference
5. At here, could FS be triggered to terminate the conference?

Regards

Scott