how to stop a movieclip on the Y-axis with buttons? - actionscript-3

Question

I have two buttons that moves a movieclip up/down the Y-axis. How do I get the movieclip to stop at a certain height, and still be able to move it in the opposite direction?
I need this to work like this:
When you press the down-button, the movieclip goes downwards, but not past Y=500.
When you press the up-button, the movieclip goes upwards, but not past Y= 300.
I get the movieclip to stop at the correct point (500), but when it reaches this point it's stuck..
so it won't go upwards again if I press the up-button.
can someone help me please?:)
here's my code so far:
1) decrease = the down-button
2) increase = up-button
3) stempel = the movieclip I want to stop on the Y-axis
var moveStempel = 0;
decrease.addEventListener(MouseEvent.MOUSE_DOWN, decreasePressed);
decrease.addEventListener(MouseEvent.MOUSE_UP, removeEnterFrame);
increase.addEventListener(MouseEvent.MOUSE_DOWN, increasePressed);
increase.addEventListener(MouseEvent.MOUSE_UP, removeEnterFrame);
function decreasePressed(e:MouseEvent):void
{
moveStempel = 2;
addEnterFrame();
}
function increasePressed(e:MouseEvent):void
{
moveStempel = -2;
addEnterFrame();
}
// ADD ENTER FRAME
function addEnterFrame():void
{
this.addEventListener(Event.ENTER_FRAME, update);
}
function removeEnterFrame(e:MouseEvent):void
{
this.removeEventListener(Event.ENTER_FRAME, update);
}
function update(e:Event):void
{
if (stempel.y < 500)
{
stempel.y += moveStempel;
trace("inside");
}
else if (stempel.y > 500)
{
stempel.stop();
trace("outside");
}

Answer 1

In your code right now, once stempel has a y value greater than 500, it will never be able to move again.
There are two conditions when stempel can move: if it's moving down, it can't be at the bottom of the allowed area, and if it's moving up, it can't be at the top of the allowed area.
if ((stempel.y < 500 && moveStempel == 2) || (stempel.y > 300 && moveStempel == -2))
{
stempel.y += moveStempel;
trace("inside");
}
else
{
stempel.stop();
trace("outside");
}