why are you doing this??? trying to play a message when people call a user, but they can't leave a message?
if so, in VM pro:
1. create a module, named Message
2. start point tied to generic action, add prompt for message. Record prompt. If message is going be changed regularly, create a recording module with menu action tied to editplaylist action to permit easy re recording of prompt. Give Sc access to recording module to whomever is supposed to record it.
3. create a SC *60 (or whatever) / Voicemail Collect / "Message"
4. for user, forward unconditional all calls to *60. disable VM for the user.
in short, don't use a mailbox at all.
GB