attachMovie path issue!

I have an MC in my movie that has lots of tweens and stuff in it.
It stops at a certain point, and at this point
I want to attach another MC.
So I placed an empty clip on that frame, and called it with a
button on the main timeline:


on (release) {
container.play();
_root.container.content.attachMovie("clip1", "mc1", 1);
}

But when I trace “content”, it returns “undefined”.
I’ve checked the instance name, but Flash just can’t find it.

Anyone have a clue why this is, and what to do about it?

Thanks!