var NN3 = false;

image1= new Image();
image1.src = "media/btn_alas.gif";
image1on = new Image();
image1on.src = "media/btn_alas.gif";

image2= new Image();
image2.src = "media/btn_performe.gif";
image2on = new Image();
image2on.src = "media/btn_performe.gif";

function on3(name)   {
        document[name].src = eval(name + "on.src");
}
function off3(name)  {
        document[name].src = eval(name + ".src");
}
NN3 = true;

function on(name)  {
        if (NN3) on3(name);
}
function off(name)  {
        if (NN3) off3(name);
}