videoPlayer.source = root.loaderInfo.parameters.url;
return;

This works with the standard video player component in Flash CS3.
Throw this actionscript in the first frame.  Name your video player "videoPlayer" within Flash.

Then in the HTML markup object tag:
param name=FlashVars value="url=PathToVideo.flv"

Then in the HTML markup embed tag:
FlashVars="url=PathToVideo.flv"

Dynamic Flash video

flash, video

ActionScript