How to setup a conference room as a resource only in Outlook 2003, Active Directories, or Exchange 2003

I am setting up a conference room as a resource in Outlook.  Is there a way in active directories, exchange 2003, or outlook 2003 that I can set up this mailbox as a resourse only?   When "planning a meeting" in outlook, it works fine when you choice the conference room as a resource.   When you add the conference room as an attendee, it does not notify the organizer if it is busy, etc.   I would to remove the ability to add the conference room as an attendee and only be able to choose it as a resourse.  Is that possible?