If you are capturing your DV thru firewire, then the answer is no. A Firewire capture is really just a file transfer, so there is no actual "capturing" going on. It is the same as if you were copying a file from a zip disk or other data storage.
You could place your captured video event in the timeline, then hit the "arm for record" button on an audio track, and record your voice with a microphone while the event is playing.
might be worth checking out scenalyzer: can capture dv/audio stream to avi in one file and another channel 2 audio stream simultaneaously off the cam if it has been recorded with two audio sources...