Check width of movieclip loop?

Hey all,
I have a frame that plays and checks and prints the width of a movieclip, but the movieclip is constantly changing size, so I would like the textfield to show the movieclip width as is scales. I would assume I need to create a method of looping the code that checks the width, maybe a setinterval?

 
 
ypos.text = (this.rulerslave.picture_mc._width);
xpos.text = ("1");

stop();

That’s what I have on the current frame. Any ideas? thanks guy