Passing MC name in array, then modifying MC

Here’s my question. I am storing the names of a bunch of dynamically made MC’s in an array. I then want to pull out the corresponding one to the current position, and change the mc’s alpha.

If I trace the the array,

trace(_root.mcNameArray[_root.arrayposition]);

I get the correct MC location

_root.nav.galleryloader.main.mc21

Now, how can I take that value and modify it’s alpha? I want to take that MC by having something like this:

onClipEvent(enterFrame){
_root.mcNameArray[_root.arrayposition]._alpha=20;
}

But it does not perform the alpha change. Any ideas?

Thanks!