Controlling a parent swf from the child

I have a main.swf. Into this I'm loading a background.swf
The background.swf contains a masked image. What I want to
do is stop the parent (main.swf) while the preloader and image load from background.swf
I've tried playing about with _parent.stop but unfortunately
this is stretching my vast flash experience to the limit already.

Any help or links would be very welcome.

Cheers guys/girls.

Have you tried _level0.stop();?

Cheers for that.

_parent._level0.stop();

did the trick