Unload movies

I’m sure this must be very easy but I haven’t been able to sort it out!
I simply want to unload a swf that I’ve loaded in a movieclip (I’m trying to unload it from another movieclip on same scene, same level).
So first I load the movie on level 1, thinking that I could unload level 1 from any other place. But it didn’t work. (I can load but not unload)
on (release) {
unloadMovieNum(1);
gotoAndPlay(50);
}
So then I’m loading the movie in an empty mc (container) but unload still not working.
on (release) {
unloadMovie("_root.container");
gotoAndPlay(50);
}
I’d believe it is the path wrong as I tried hiding it by using set property and didn’t work either. Any ideas? Many thanks.