create movieclip in anothher class

[Flashlighting]

Hi everybody...
I'm pretty new in AS3...

In class A I write

[...]
public class A extends MovieClip
    {
        public function A():void {

        public static var menuContainer:MovieClip;
                menuContainer = new MovieClip();
        addChild (menuContainer);
        menuContainer.y = 200
[...]

In class B I write

[...]
var p:menuItem_mc = new menuItem_mc()
Main.menuContainer.addChild (p)
[..]

And this works fine.

But I would like to move all the code belonging to the menu to class B...
so I commented all the code above in class A and in class B I wrote:

var p:menuItem_mc = new menuItem_mc()
var Main.menuContainer:MovieClip;                     
Main.menuContainer.addChild (p)

but I got the following error:
TypeError: Error #1010: A term is undefined and has no properties.
at Menu$/deployMenu()

So...my question is: how can I create a movieclip in another class and add a child to it?
thanks,
Adam