I'm trying to change the class of certain tags with a certain className...

I'm using MooTools as the framework...

My code:

Code:
    var arrElements = document.getElementById('audio_inner').getElementsByTagName('a');
     for(var i=0; i<arrElements.length; i++){
        if (arrElements[i].className == 'select_bold') {
            var rid = arrElements[i].id;
            $(rid).toggleClass('select_normal');
        }
     }
I have tested arrElements[i].className and arrElements[i].id and they seem to send the correct values but it won't toggle the class....

I even tried replacing $(rid).toggleClass('select_normal'); with document.getElementById(rid).className = 'select_normal'; just incase it was a MooTools error.

Any idea's what is wrong with my code?