SendDTMF and Broadvoice

Broadvoice has a feature that allows you to take an incoming call from the outside, dial out to another number from the inside and then either remain connected, in three way calling, or terminate the call and leave the two external users connected to each other, in the process removing yourself, and your phone lines, entirely (i.e., you could unplug the asterisk box and the two outside would be unaffected). So…this is done (using a standard broadvoice setup) by sending a flash, dialing, sending another flash and hanging up. So…with asterisk, how do I do this? I’ve been trying to figure out how SendDTMF works, and i’ve determined that a DTMF code of 16 is a flash, but how on earth do I use this to flash the broadvoice trunk? Any help on this would be greatly appreciated.