var CENTER:Number = stage.stageHeight / 2;
var SPEED:Number = 1/10;

var mc:MovieClip = blah_mc;

addChild( mc );

addEventListener( Event.ENTER_FRAME, onEnterFrameHandler, false, 0, true );

function onEnterFrameHandler( e:Event ):void
{
	var distance:Number = mouseY - CENTER;
	mc.y -= ( distance * SPEED );
	if( mc.y > 0  ) mc.y = 0;
	if( mc.y < -stage.stageHeight ) mc.y = -stage.stageHeight;
}

Here's a way to scroll items using mouseY

AS3: MouseY Scrolling

ActionScript 3