MeetMe and the Set Marked User

Iam using the business edtion of asterisk

version is 1.4.x ( )

In the asterisk gui we have option of the set marked user in conferencing section.

Iam trying to use that feature , it seems to no provision in the gui to set that.

I tried by seeing from the server point of view ( browsing the meetme.conf and user.conf etc )

Still i could not able to find how to set that user…?

Any ideas and advices would be appreciated.