Looping through MCs and unload

Hi

I am back again with another problem!!
first, I have an emptyMovieClip which I attach other mcs to it,shouldn't a mc get unloaded when I attach a new one? (I think it should!) and it works fine but when I call another function ( which is a basic duplicate function that duplicates some mcs), my mcs don't get unloaded and I don't understand why? so if anyone can explain that to me it would be great.

but for now I am going to use a loop to make sure all the mcs get unloaded,
my mc (instance names) are something like this: mc1,mc2,mc3...(so i=1,2,3,..)
and my loop is:

for(n=1; n<=i; n++)
{

_root.mcHolder.mc+n.unloadMovie();
}

but this doesn't seem to work, the problem is that mc+n won't return the right value(which should be mc1,mc2,mc3....).

any idea what I should replace it with?

Thanks in advance.