Does anyone have a hack or know how to make the Treo 300 auto-answer phone calls with the headset in?

I am in a desperate search for this funcionality so that I will be able to take phone calls while on my motorcycle. I have an intercomm system that will plug into the headset jack via a 4-pin 2.5mm connector, but I can't make the phone auto-answer once connected.

Every other cell phone I have had could do this...but the Treo can't?