Last clicked button

this doesnt work any more and its pissing me off, I used this before and it always worked…

var lastClickedButton:MovieClip=null;

function scanChange(e:MouseEvent):void {

    if (lastClickedButton!=null) {

I use movieClips, not Objects and I get this error while compiling:

1118: Implicit coercion of a value with static type Object to a possibly unrelated type flash.display:MovieClip. and it points to this line:;

and if I say this:

var lastClickedButton:Object=null;

I get this weird error while compiling
in the output window:

TypeError: Error #1016: Descendants operator (…) not supported on type flash.display.MovieClip.
at newvideo38_fla::MainTimeline/newvideo38_fla::frame1()

and I am not using any double dot nowhere…