I've never done it, but I would imagine it involves the pro only feature render to texture. I don't know if turning the movie file into an animated sprite would work or if you'd run into a huge, unusable or inefficient for use animated sprite file, though. Maybe, with luck render to texture will trickle down to commercial when A7 arrives (c'mon Conitec that would be great, but what would we have to sacrifice to get this...BSP had to go pro to get unlimited physics in commercial).