I havnt installed my D3 yet just ordered it last night but I have ran into a similar issue when I am using my headset. Since I only check my Voice mail when I have new VM, I created a Phone Book Entry called V. Mail. The number is *86p#XXXXp1 . Now I have Verizon so *86 dials the voicemail service p pauses until it hears audio from the system then sends #XXXX (XXXX is the password for the mail box) Then it pauses again Then sends a 1 that is the command for Playback new messages.
I know this is not exactly what you want but it is a work around that I use.