A little more information on your inquiry will be necessary to answer anything other than a simple....YES!

But let me take a guess at what you intended to ask...

It is possible to add a 'director's commentary' track to a finished video and encode it onto a DVD with DVDA?

Yes you can record the commentary in real time onto a separate track in Vegas while replaying vision and associated audio out to the 'director'. I'd recommend feeding the sound to the director on headphones not speakers.

Assuming your audio interface has a microphone input select a suitable mike and arm a new track in Vegas for record and select the correct input for the mike.

More info on doing this is available in the Vegas help files.

Once the commentary is recorded you can mix it as a new mix with the original sound track of the video mixed under the commentary.

Render the new mix to either WAV or AC3 for DVD.

In DVDA import your media, vision, full sound track and the director's commentary sound track,
Add the normal vision and full mix sound the timeline and then create a second audio track and place the director's commentary mix on it.

Note having ALL three tracks rendered from the exact same start point makes synchronising them simple.

If you want you can create menu buttons to select between the two audio tracks, full mix and director's commentary, but even if you don't viewers can still switch between tracks using the DVD player remote's audio functions.

Obviously menu selection is the best option though.

If that didn't answer your question can I suggest you frame it more succinctly next time.

New Hope Media