Accessing the buttons on the stage


I am facing a problem while i am trying to access the Button object on the stage…
I am writing the function I am using…

function progressHandler(event:VideoProgressEvent):void
var bl = Math.round(event.bytesLoaded/1000);
var bt = Math.round(event.bytesTotal/1000);
var time:Number = (bl/bt)*display.metadata.duration;
var cc = display.findNearestCuePoint(time)
if (cc != null){
trace("_btn");// This gives me the instance name of the button.
// Now, how can I play with the properties of the
// button. ‘this’ here gives the main timeline…

Thanks for any help that can be provided…