var n3 = false;

image2       = new Image();
image2.src   = "images/menu/nav_02.jpg";
image2on     = new Image();
image2on.src = "images/menu/roll_02.jpg"

image3       = new Image();
image3.src   = "images/menu/nav_03.jpg";
image3on     = new Image();
image3on.src = "images/menu/roll_03.jpg"

image4       = new Image();
image4.src   = "images/menu/nav_04.jpg";
image4on     = new Image();
image4on.src = "images/menu/roll_04.jpg"


function on3(name)
{
    document[name].src = eval(name + "on.src");
}

function off3(name)
{
    document[name].src = eval(name + ".src");
}

n3 = true;
function on(name)
{
   if (n3)
      on3(name);
}

function off(name)
{
   if (n3)
      off3(name);
}