How to clear a timeout

Hi.
I need to clear a timeout in another movieclip.
I use the clearTimeout directive in _root. and doesn't work. I need it to work from _root.

Example:

button_btn.onRelease = function() {
_root.clearTimeout(_root.content_mc.my_timeout);
}

And it doesn't work.

Has anyone any ideas how it should be written?

Thanks.