Are you going to the "normal" auto attendant of Embedded/Express VM? Typically you would program nothing and in form 19 for the tenant of the trunks, send DID Vacant Number Routing to the VM hunt group.
It might be worth it to consider reprogramming this to make use of the DID Assignment form, it is pretty easy, you can build Form 55, then after everything looks good, just change the insert digits on the trunks and this will never be a problem again.