Centering a movie inside a draggable window

I have a draggable window that is placed in a movie at the level 3. I have a button in level 0 that when I pressed it will load a movie into the draggable window. I want the movie to be centered into the window because I have a drag bar and it will look nice if the movie is centered. So far I was able to load the movie but since it loads into the left upper corner the bar sometimes look small and not in the center. What should I do?
Your help is appreciated.
Thank you
Carlos