The only way I know to do this is with a script. I think the original one came with Vegas, but I made a lot of changes, most of which were designed to make the Render Regions part of the program work better. It is posted over at VASST:
But here's the weird part. I go back to where he told me, in V5 ( which I'm still using ) Tools-Scripting-Batch Render.......but it's gone ????? The Batch Render tool is anyways.
Anyone know why it would be gone and if I can put that back ?
Do a search on your whole computer for files that end in "js". In other words, search for:
*.js
You should find the location of all the script files (some of these will be stuff that your browser downloads and will be in the temporary folder -- ignore those). You should find that the files that appear in your scripts folder are all in one location. The batch render script may, for some reason, not be in that folder. If so, all you have to do is move it to the location where the other scripts reside, and then tell Vegas to "rescan the scripts folder" (you'll find this option in the scripts menu).