Error #1006 Value in not a function... SOLVED BUT it's the right way?

[Americanhorizon]

Hi i've this simpel code

var ter: terms=new terms()
addChild(ter)
ter.name="termini"


(getChildByName("termini") as MovieClip).scroller.barra.addEventListener(MouseEv ent.MOUSE_DOWN, scrollatermini)

but when i launch it flash give me error 1006: value is not a function..

I've solved converting all in MovieClip

MovieClip( (getChildByName("termini") as MovieClip).scroller.barra).addEventListener(MouseE vent.MOUSE_DOWN, scrollatermini)

I ask to you that are expert than of me: is it the right way to do this?