I am assuming you are talking about an auto attendant. If so, you need to build a "Cal l Handler" in Unity where you can upload/record the desired greeting, assign a schedule, and map caller input to desired destinations. In CUCM you need to create CTI Route point with an extension that is set to call forward all to voicemail, the extension needs to be the same on Unity and on the voice GW you need to point the calls to CUCM. If you have FXO trunks that need to ring into this AA then on the voice-ports configure "plar opx XXXX" where XXXX matches the extension, and matching dial-peer that points to your CUCM (assuming SIP or H323 protocol is used to control the GW, if MGCP then use attendant DN field in CUCM FXO port configuration).
