function gestor() {
    var enviarNuevoDisabled = !document.loginform.nuevo.checked;
    var enviarDisabled = !enviarNuevoDisabled;
    
    document.loginform.enviarnuevo.disabled = enviarNuevoDisabled;
    document.loginform.enviar.disabled = enviarDisabled;

    var boton1 = (enviarNuevoDisabled) ? "boton" : "boton1";
    var boton = (enviarNuevoDisabled) ? "boton1" : "boton";

    changeOpac("60", boton1);
    changeOpac("100", boton);

    if (enviarNuevoDisabled) {
        document.loginform.enviarnuevo.style.cursor = "default";
        document.loginform.enviar.style.cursor = "pointer";
        document.loginform.usuario.focus();
    }
    if (enviarDisabled) {
        document.loginform.enviar.style.cursor = "default";
        document.loginform.enviarnuevo.style.cursor = "pointer";
    }
}

window.onload = function() {
    gestor();
}

function listen(elem, event, func) {
    if (elem.addEventListener) {
        elem.addEventListener(event, func, false);
    }
    else if (elem.attachEvent) {
        var r = elem.attachEvent("on" + event, func);
        return r;
    }
    else throw 'No es posible aņadir evento';
}

listen(window, "load", function() {
    listen(document.getElementById("registrado"), 'click', gestor);
    listen(document.getElementById("nuevo"), 'click', gestor);
}
	);

function changeOpac(opacity, id) {
    var object = document.getElementById(id).style;
    object.opacity = (opacity / 100);
    object.MozOpacity = (opacity / 100);
    object.KhtmlOpacity = (opacity / 100);
    object.filter = "alpha(opacity=" + opacity + ")";
}