Use this Action to unload a .swf file that was previously loaded in a specified level.
Source
This variable determines whether the Movie should be unloaded from a particular level or Sprite. See the Load Movie Action for more information.
Level (unloadMovieNum)
You can specify the Movie level that you want unloaded. Any .swf Movie playing in that level is cleared.
Sprite (unloadMovie)
You can specify the Sprite that you want unloaded. Any .swf Movie playing within that Sprite is cleared.
