Sorry. I had to re-read your post a little more carefully.
I have a couple of additional questions.
Your receptionist, is it a console or a phone?
When the diverting a call via call rerouting, are you routing to a key on a console or a hunt group?
In general, I think if you simply forward whatever number you're rerouting to on RNA or Busy, reroute that number in night1 and Night2 directly to voice mail. As long as you don't have some strange class of service or hunt group, the call should end up in the mailbox of the extension that was originally called.
Ralph