jQuery.validator.addMethod("valore", function(value,element,params) {

  var currentValue = value;  // oppure element.value
  if (element.type == 'radio') currentValue = $("input[name='"+element.name+"']:checked").val();
  return value == currentValue;
      
},jQuery.validator.format("Controllare il campo / Check field"));
//jQuery.validator.format("attenzione !!"));
//jQuery.validator.messages.required);