Please help; next btn and onSoundComplete()

Hi,

Can someone help me form tearing out any more hair? The following code should work but it is not, it should play the next song:

this.sound_obj.onSoundComplete = function(){
(song_nr==songfile.length-1)?_global.song_nr=0 : _global.song_nr++;
_root.sound_mc.songStarter(songfile[song_nr], songname[song_nr]);
};

I have it also attached to a Next button, as follows;

next_btn.onRelease = function(){
(song_nr == songfile.length+1) ? _global.song_nr=0 : _global.song_nr++;
_root.sound_mc.songStarter(songfile[song_nr], songname[song_nr]);
};

The XML code is as follows;

?xml version='1.0' encoding='utf-8'?>
<songs>
<song name="i-tuts" file="ituts_track.mp3" ><song />
<song name="test2" file="test2.mp3" ><song />
</songs>

Any help, will greatly reduce hair loss ;)

Boxing Boom