Weblabor

Event.observe(window, 'load', windowInit, false);

function windowInit(){
    var testForm = Form.getElements('testForm_2');
    testForm.each(
        function (elem,index){
            new Form.Element.EventObserver(elem,checkField) ;
            if (!elem.id) elem.id = 'testForm_2__'+index;
        }
    )
}

function checkField(elem){
    name = elem.name;
    var checkBoxes = $A(document.forms.testForm_2).findAll(
        function(checkBox){ 
            return (checkBox.name == name && checkBox.checked);
        }
    )
    
     checkBoxesQueryString = checkBoxes.collect(
        function(checkBox){
            var checkBoxObject = function(name,values){this[name] = values;}
            var checkBoxes = new checkBoxObject(checkBox.name,checkBox.value);
            return $H(checkBoxes).toQueryString();
        }
    ).join("&");
       
    console.log(checkBoxesQueryString);    

}