[jQuery-Form Validator] Problem with Rules

[jQuery-Form Validator] Problem with Rules

Hi guys.
This is my code:
  1. $().ready(function() {
            $("#previ").validate({
                    submitHandler: function() {
                     if(confirm('Sure?')){
                            $(form).submit();
                            return true;
                      }else{
                             return false;
                     }
                    },
                    rules: {
                            id_previsione: { required:  true },
                            id_icona: { required: true },
                            id_regione: { required: $('#id_previsione').val() == 1 }, //NOTE
    THIS ROWS <-----
                            testo_previsione: {     required: true  }
                    },
                    messages: {
                            id_previsione: { required: "is required.." },
                            id_icona: { required: "is required..."},
                            id_regione: { required: "is required..."},
                            testo_previsione:  { required: "is required.," }
                    }
            });
    });

























I don't riceve any error but it doesn't work as i expected.
I want that the rules id_regione { required: true } is applyed when
the val of id_prevision is == 1.
Understand my problem?
Many Thanks.
Best regards.