function gupOver(evenet:MouseEvent):void {	
	for(var i:Number=0; i<10; i++){
			if(thumbContainer_mc.y >= 166) {
				thumbContainer_mc.y -= i;
			}
			else {
				break;
			}
		}
	}
}
			
function gdownOver(event:MouseEvent): void {	
	for(var i:Number=0; i<10; i++){
			if(thumbContainer_mc.y >= 290.9) {
				stop();
			}
			else {
				thumbContainer_mc.y += i;
			}
		}
	}
}

error
TypeError: Error #1010: A term is undefined and has no properties.
	at main_fla::MainTimeline/gdownOver()