I had a hard time finding a way to stop a sprite, so I figured I would post it.
     $button = new SWFButton();
     $button->addShape($box, SWFBUTTON_UP | SWFBUTTON_HIT | SWFBUTTON_OVER | SWFBUTTON_DOWN);
     $button->addAction(new SWFAction("
          setTarget('box');
          stop();
      "), SWFBUTTON_MOUSEUP);
     
     $item = $movie->add($button);
This works the same way with play();