function show_hide_fields() {
  var rows = "tr.first-name, tr.last-name, tr.phone, tr.address1, tr.address2, tr.city, tr.province, tr.country-field";
  var fields = "#tbLastName, #tbAddress1, #tbCity, #ddlCountry, #ddlProvince";
  if ($("#cbPrintedGuide").is(":checked")) {
      $(rows).show();
      $(fields).addClass('required');
  }
  else {
      $(rows).hide();
      $(fields).removeClass('required');
  }
}