Manipulating MCs attached to other MCs

How do you address a mc attached to another mc?

I have an array of movie clips some of which I have attached additional movie clips to. Now I need to alter scale/alpha etc of those additional movie clips.

ie.

for (i=0;i<BasicMCArray.length;i++) {
_root.BasicMCArray*.attachMovie(“myExtraMc”,“ExtraMC” + i,depth++);
}

How do I now manipulate the “ExtraMC” movie clips? I know I can use
_parent to get at the parent mc but how do I get at the “child” when names are dynamically created as above?

Any advice would be much appreciated!