Help targeting a button within an MC from another MC - Erro 1061 ALL DAY

I know what the error 1061 means, but have no idea how to fix it. I’ve tried to correct it a million & one ways…

1061: Call to a possibly undefined method getChildByName through a reference with static type flash.display:DisplayObject.

I’m trying to target a button named ‘mcTargetButton’ (a SimpleButton) that’s inside a movie clip called ‘mcTargetParent’ from a movie clip called ‘mcCallFromThisClip’.

Both clips are on the main timeline. Note, I am using a document class… if I trace (this.parent) from ‘mcCallFromThisClip’ it prints the name of the document class.

trace(this.parent.getChildByName("mcTargetParent")); // traces 'mcTargetParent', yea!

Trying to go one step further to reach the nested button, Flash shows no love.

trace(this.parent.getChildByName("mcTargetParent").getChildByName("mcTargetButton")); // traces 1061 above

Apparently, no matter how I try to cast the button… Object, DisplayObjectContainer, Sprite, MovieClip - I will still get the 1061.

Any ideas, how hard should it be to reach a button from a different movie clip?