Asterisk Outbound Dial to AA, Detect Silence

We currently have an Trixbox asterisk box that will make an outbound call, and then connect that call to an auto-attendant (IVR) or to an extension... Whatever we want. However, we want to be able to leave a message for the person should they not pick up. We have attempted to use AMD and WaitForSilence, but it doesn't seem to work. I'm looking for a coder who can SSH into our system and make changes as necessary. Furthermore,? we require the work to be documented fully from the basic trixbox installation to the completed solution. We expect the documentation to be in US English with step-by-step instructions.? ? ? ? ? ? ?