Help please. Trying to show Object from hiding using Key Press

So I've try and try, but fail to get it right. I'm trying make Button/Object reveal itself from hiding
Got the button to be false and now Im trying get where a keystroke.. let say "j" to get the button to come true

Button.visible = false;

stage.addEventListener(KeyboardEvent.KEY_DOWN, fl_KeyboardDownHandler_4);

function fl_KeyboardDownHandler_4(event:KeyboardEvent):void
{
trace("j" + event.keyCode);
Button.visible = true;
}

Clearly I'm doing it wrong. I think I'm suppose to add a event for the hidden object. I've done different ways, but none works. Anyone know how I could get this to work? It be very awesome if anyone can help.

Would also like to know if there a way to do it using more than one keystroke. Like is it using + or == ?