Need help detecting if external movie is loaded

1

Here is the situation, when you click on a button an external movie clip loads into an empty movie clip located on the stage easy enough. Now I am trying to make it so if you were to click the button again while that same movie is still loaded in the empty movie clip the button knows not to load the movie again. Can anyone help me out or direct me to a tutorial related to this, as everything I tried so far is not working. Thanks!