removing movie clip

I have a "content_mc" on the main timeline that is created by .attachMovie (). Inside the "content_mc" i have a button that I would like to close (removieMovieClip ()) the content window. Here is the code I have.

Maintimeline:
function buildContentBox () {
this.createEmptyMovieClip("content_holder", this.getNextHighestDepth());
content_holder.attachMovie("content_mc", "content_mc",this.getNextHighestDepth(),{_x:185, _y:185});
} // which is called by a button action and works ok

Inside the content_mc

close_btn.onPress = function () {
_root.content_holder.content_mc._x += 10;
_root.content_holder.content_mc.removeMovieClip();
} // the _x is to see if I am hitting the _mc correctly - the clip moves to the right on press, but does not delete

Any help to what I am doing wrong would be appreciated.

W.