Working on a project with billboards..

I just click on the window explorer/folder/file and drag it into the billboard of the project.

It appears the wmv loads in fine and works. I built a couple of loops in Sony Vegas to import into the project.

Is there a way to play the loops or do I have to make a complete video for the duration of the video. Yes, I can do it with the timeline, but I was wondering if there is an easier way.