Action Script 2.0 Check Mouse Direction

// This code is for Action Script 2.0
checkX = function (dx, oldVal, newVal)
{
    if (oldVal<newVal)
    {
        trace("moving right");
    }
    else if (oldVal>newVal)
    {
        trace("moving left");
    }
        return newVal;
    };
        checkY = function (dy, oldVal, newVal)
    {
    if (oldVal<newVal)
    {
        trace("down");
    }
    else if(oldVal>newVal)
    {
        trace("up");
    }
    return newVal;
};

this.watch("xdir", checkX);
this.watch("ydir", checkY);

this.onMouseMove = function()
{
    xdir = _xmouse;
    ydir = _ymouse;
};