Click and object appears as top-most layer

As written in the title, how do I make this work?
I need step-by-step tutorial, so please give me some help here (:

An example:
http://www.y8-games.net/games/Sandwich_Maker

At the left side, see the bread and all the ingredients?
When you click on any one object, it appears on the top most.

Yeah, that's what I want to know.
Hope someone will help me. Thanks.

*edited*
PS I'm using AS2 (:

AS2 or AS3? If it's AS3 then

PHP Code:

---

someobject.addEventListener (MouseEvent.MOUSE_DOWN, onMouseDown, false, 0, true);
function onMouseDown (e:MouseEvent) {
    e.target.parent.setChildIndex (e.target, e.target.parent.numChildren - 1);
} 


---

That's how you can do it in general.

e.target is the object that caused the event listener to go off, in this case it's someobject.

.parent is the parent of whatever is in front of the dot, so it's the parent of the target that set off the event listener.

setChildIndex (object, index) is a displayobjectcontainer's method that pretty much moves its children from top to bottom or vise versa, an index of 0 is the very bottom, you set it to e.target.parent.numChildren - 1 so the index will be however many children the container has minus 1 so it'll always be on top, minus 1 because it's zero-indexed.

I'm sorry, but I'm a beginner in this... Could you pls elaborate on where I gotta place this script at? Do I need to change anything to the instance's name or anything like that?

Thanks!