Controlling an button's alpha with if/else

I have an emptyMovieClip and a button on my stage. I’d like to control the alpha of the button depending on whether a movieclip is loaded into the emptyMovieClip or not. I’m just a beginner at Flash and have little programming experience.

if a movie is loaded in the emptyMovieClip, button alpha = 100%

else button alpha = 0%

I know. It’s a sorry attempt . . . :frowning:

Can someone help?