Button component label probs

Hello again.

Im attaching a movieclip that ONLY contains a button (from the component library).
the movie is called extra en exported in the first frame.
The button in the “extra” mc, has the instancename “extraKnop”.
The xml works fine since it acctually attach the extra mc.
I did a trace on _name and a trace on _parent (from within the extra mc), it traced the right name and level0.

if (this.childNodes[0].childNodes*.childNodes[1].firstChild.nodeValue == "extra") {
               //attachmovie extra meuk
               attachMovie("extra", "extra"+extraNr, i, {_x:speler._x, _y:hoogteMask2+i*18});
_root["extra"+extraNr].extraKnop.label = "test";//that wil be something else from the xml file later (when it works) 

As you can see in the As code, the “label” isnt working…why…

Is there something I dont know yet about components so that will the answer, or do i miss something else ?

thx in advance.