function checkAllBoxes(obj,pref) {
	if(document.getElementsByTagName){
        var inputs = document.getElementsByTagName("input");
        for (var i=0;i<inputs.length; i=i+1) {
	            if(inputs[i].type == 'checkbox' && inputs[i].checked != obj.checked && pref == inputs[i].name.split('[')[0]){
	                inputs[i].checked = obj.checked;
	            }
        }
    }
   
}