Hide Button (added in onLayout) in onUpdate

I'm developing an app for my VivoActive 4 which currently has a Button containing a bitmap, which is added via onLayout(dc) so I can set/handle a `behavior`... 

    var myBtn = null;
    function onLayout(dc) {
        var elements = [];
        var myBitmap = new WatchUi.Bitmap({:rezId=>Rez.Drawables.MyIcon});
        myBtn = new WatchUi.Button({
            :locX=>50,
            :locY=>50,
            :width=>50,
            :height=>50,
            :stateDefault=>myBitmap,
            :stateHighlighted=>myBitmap,
            :behavior=>:onBtnClicked
        });
        elements.add(myBtn);
        setLayout(elements);
    }

Is it possible to hide/remove the button and/or image after the onLayout has run?

I've tried accessing either the button or the image within `onUpdate(dc)` but I simply cannot figure out a way to get it to disappear in response to an action.

Can somebody please point me in the right direction.

Cheers,

Tom