Sure, you'll first need to create a "phantom" hunt group, with no members. It can be any unused directory number, and probably something outside your typical extension range. One thing you'll have to test is if the hunt group type should be voice or nametag. I'm suspecting you'll want nametag, but I've had issues with that in the past.
Next, in the call re-routing forms always form you'll need to create a voicemail re-direct number. (This may already exist, and if so, no reason to re-invent the wheel.) Pick an unused reference number, set all the options to "this" and put the voicemail pilot number as the directory number. Now go into Call Re-routing assignment, and set Day/Night1/Night2 to the reference number you just created.
Now if you call your phantom hunt group, it should ring to voicemail and play the auto-attendant greetings.
Finally, you need to create your "9" voicemail box. When creating, you need to set the mailbox type to 'transfer only.' Your mailbox number would be 9 and the extension number would be your newly created phantom hunt group. {Keep in mind that if 9 is used by your auto-attendant for the dial-by-name directory, you'll have to use something else.}
