Fade in volume on dinamic songs

1

hello there, i want to make a fade volume between songs to songs…
this is the function i have made… what’s wrong?

fade.onEnterFrame = function() {
        new_volume = 0;
        var sameVar = setInterval(fadeIn, 5000);
        function fadeIn() {
            if (new_volume<=100) {
                new_volume += 3;
            } else if (new_volume>=100) {
                new_volume = 100;
                clearInterval(sameVar);
                delete fade.onEnterFrame;
            }
        }
    };

thanks