Replacing default external w/ button click

Question

My container (emptyMC) will load 4 external movies and loop as
default when someone comes to the site.
Right now the code for the empty mc (emptyMC) is:
var loader:MovieClipLoader = new MovieClipLoader();
this.createEmptyMovieClip("emptyMC",1);
loader.loadClip("image1.jpg",emptyMC);
It loads the sample default image great.
What needs to happen is when someone clicks Button1, Button2, Button3, or Button4,
(which are movie clip buttons) the corresponding movie needs to load on the click of the button
in the empty movie clip (emptyMC) and replace the default movie loop.
Movie Loop default plays in "emptyMC" at entrance of site
Button1 is clicked, Movie Loop default is replaced in "emptyMC" with Movie1
Button2 is clicked, Movie Loop default is replaced in "emptyMC" with Movie2
Button3 is clicked, Movie Loop default is replaced in "emptyMC" with Movie3
Button4 is clicked, Movie Loop default is replaced in "emptyMC" with Movie4
These are all external files.
Thank you so much.

Answer 1

The image will load but I lose the down state with the filled box indicating the current selection.
Here's how the button mc is:
On the main stage there's 4 button mc's (Button1, Button2, Button3 Button4)
They are all on the same frame.
-double click to edit the movie clip-
Layer 1
Frame 1: box outline
Frame 6: box outline w/ "x"
Frame 11: box outline
Classic Tween between each set of frames
Layer 2
A button with this code:
on (release) {
    if (_root.Button1._currentframe == 6) {
        _root.Button1.gotoAndPlay(7);
    gotoAndPlay(2);
on (release) {
    if (_root.Button2._currentframe == 6) {
        _root.Button2.gotoAndPlay(7);
    gotoAndPlay(2);
on (release) {
    if (_root.Button3._currentframe == 6) {
        _root.Button3.gotoAndPlay(7);
    gotoAndPlay(2);
on (release) {
    if (_root.Button4._currentframe == 6) {
        _root.Button4.gotoAndPlay(7);
    gotoAndPlay(2);
and then
stop(); (for Layer 1's Frame 1)
stop(); (for Layer 1s Frame 6)
gotoAndPlay(1); (for Layer 1s Frame 11)
Classic Tween between each set of frames
This is working great. I go to the main stage and add this code to the actions
layer in frame 3:
Button2.onRelease = function()
     loader.loadClip("image2.jpg",emptyMC);
and I lose the down (filled box) state.
I'm really lost...
Thanks for helping me out.