You could make your borders in photoshop over a transparent background and import it to Vegas. If you put this on a track, anything below it should be visible through the transparent areas of your graphic (that you can crop with Event Pan/Crop tool to your liking).
Once you’ve got the border graphic the way you want, put your videos in tracks below it and use Track Motion or Event Pan/Crop to position them with the transparent areas of your border graphic.
If you have any problems with transparency, just make it very brilliant green (or if your border is green, brilliant red or blue) in photoshop and use the Chroma Key plugin to remove it.
I hope I answered your question properly!
Daniel Hughes
Amateur Writer, Director,
Director of Photography
United Kingdom