I want to create an endless panning loop: left-right-left-right-left etc. That is, I want to shift a cropped region of a video, left-to-right, then in reverse, and repeat this endlessly, by oscillating between 2 values in X. I don't want to set repeated keyframes manually. I could write a script or a plugin, if needed. But I'm wondering if there's maybe some "algorithmic" (not explicitly keyframed) method to do this, so that Vegas would automatically oscillate/interpolate between two values in an endless loop (with a specified speed).