2 CLICK functions on 1 button

You could use a flag variable:

var:isOpen:Boolean = false;

//Eventlisteners

menu_over.buttonMode = true;
menu_over.addEventListener(MouseEvent.CLICK,onOut,false,0,true);

//Functions

function onOut(e:MouseEvent):void {

  if(!isOpen){

    menu_over.gotoAndPlay("menu_op");

    }else{
    menu_over.gotoAndPlay("menu_beneden");

  }

isOpen = !isOpen;
}

Create another variable for your movieclip as a boolean type... maybe naming it something like "isDown" if down is the initial condition.  Then in your click function have a conditional that takes an action depending on whether isDown is true or false and toggle the value to the opposite state after that.

var isDown:Boolean = true;

function onClick(evt:MouseEvent):void {

     if(isDown){

          // move up

     } else {

          // move down

     }

     isDown = !isDown;

}

Hi,

This may help you

menu_over.addEventListener(MouseEvent.CLICK,onOut,false,0,true);

//Functions
var myBoolean:Boolean = false;

function onOut(e:MouseEvent):void {

    myBoolean = !myBoolean
    if(myBoolean)
    {
        menu_over.gotoAndPlay("menu_op");
    }
    else
    {
        menu_over.gotoAndPlay("menu_beneden");
    }

}