CKEditor

Hi. I am using ckeditor and It is really great. The only one problem I have is that I am trying to use clases instead of style when align objects. More specific, I wanna use a class alignleft for align left images instead of using style="float:left". For this pourpuse I modified the plugin ckeditor/plugins/image/dialogs/image.js

In id:'cmbAlign' I changed the setup and the commid method so that it should add the class "alignleft" or "alignright" depending the situation but strangelly It does not work when I try to change the class (using removeClass or addClass, setAttribute('class') does not work too). The code is:

id:'cmbAlign',
    type:'select',
    widths:['35%','65%'],
    style:'width:90px',
    label:b.lang.common.align,
    'default':'',
    items:[[b.lang.common.notSet,'none'],[b.lang.common.alignLeft,'left'],[b.lang.common.alignRight,'right']],
    onChange:function(){
        l(this.getDialog());
        o.call(this,'advanced:txtdlgGenStyle');
    },
    setup:function(C,D){
        if(C==d){
            var E=(D.getAttribute('class')+'').match(/align([a-z]+)?/);
            if(E&&E[1])E = E[1];else E='';
            this.setValue(E);
        }
    },
    commit:function(C,D,E){        
        var F = (this.getValue()+'');
        if(C==d||C==f){
            var G=(D.getAttribute('class')+'').match(/align([a-z]+)?/);
            if(G&&G[1]){
                if(F!=G[1]){
                    D.removeClass('align'+G[1]);
                    if(F!=='')D.setAttribute('rel',F); D.addClass('align'+F);
                }
            } else {
                if(F!=='')D.setAttribute('rel',F); D.addClass('align'+F);
            }
            
        }
}

Does anybody have any idea or solution for it??