I have 2 questions about movie clips and classes.

1. Is it possible to create an empty movie clip and load into it in run time an external graphic and register the new movie clip with a class ?

2. If i load into a movie clip an external movie clip which include in it an empty movie clip and i want to change the graphics in it, is it possible to do it and how?

the following example show what i tried to do:
first load into movie clip "mc" the file "external mc"
_root["mc"].loadMovie("external mc",1);
now i want to load something into movie clip "empty" inside "external mc"
_root["mc"]["empty"].loadMovie("a new graphics mc"]);

after this command nothing change on the screen