Is there a way in Unity Conenction to play "Listen for special message" ? In our old VM system when a temporary greeting was set, and someone pressed the # to bypass the message, another message would play to ensure that a person calling in would know that the person is out of the office for a determined amount of time.
Not sure I follow 100% but here is one thought. In Unity Connection, you can do an extended absence greeting using the "Alternate Greeting" (Edit>Greetings from the end user page). Users can enable and record this greeting. When the alternate greeting is enabled, it overrides other greetings. It can be enabled with a specific end date/time or it can be enabled indefinitely. Again, user/admin choice.
On this greeting, you can configure the flag "Ignore Caller Input". I believe that this will keep users from bypassing the greeting (i.e. "#") before they leave a message. That seems to meet your need, from my understanding of the problem.