HTC 8125 / 8100 / MDA (USA) / K-JAM / P4300 (Wizard)

I am going to establish an emergency number at my business, using my current DSL phone number (being as I'm not using it for anything). I will set this number to instantly forward to my 8125. What I want to happen is have every call forwarded from my DSL number to my 8125 go instantly into voice mail where I will have an emergency intro message followed by a beep. A different voice mail alert sound would be nice, but not required. My overall objective is to be selectively responsive to my 800 clients when necessary. How, dear phonemasters can I do this?