Load MC from library

Hi all

I have a Movieclip with a base name called ‘movie_main’ and class name as ‘Main_mc’

I am trying to load the movie from the library into a contanier that also loads in a tooltip. The container is called ‘holder’

this is the script I am working with

 
var movie_main:Main_mc = Main_mc();holder.addChild(movie_main);
problem is when it loads in other parts of my menu are missed placed. 

Question:
is this the correct script I should use?? Is there issues with loading in more than 1 movieclip into one contanier??

aaarrrggggghhhhh!!!

help please