Date Problem Formule | WordPress.org

Hi

fieldname 14 : Start Date
fieldname 15 : End Date
It expresses.

My 1st question = Printing error message if fieldname 14 field is greater than fieldname 15 field.

My 2nd question: How do we calculate business days NETWORKDAYS by adding the number of days from the start date (fieldname24) to the criterion = (fieldname 23 === ‘B’)?
Can you help me complete the formula?

(function() {
  var kriter3;
  if (DATEOBJ(fieldname14, 'dd/mm/yyyy').getTime() > DATEOBJ(fieldname15, 'dd/mm/yyyy').getTime()) {  
    jQuery('#calculation-kriter3').html('Seçilen tarih ileri bir tarihdir.');
    return 'Seçilen tarih ileri bir tarihdir.';
  } else {
  if (fieldname23 === 'A') {  
    kriter3 = NETWORKDAYS(fieldname15, fieldname14, "dd/mm/yyyy");
    jQuery('#calculation-kriter3').html(kriter3);
    jQuery('.kriter3-aciklama').html('İş Günü Sayısı : ');
    jQuery('.kriter3-sonuc').html(kriter3 + ' gün');
  
  } 
  if (fieldname23 === 'B') {
    kriter3 = DATETIMESUM(fieldname14, 'dd/mm/yyyy', fieldname24, 'd');
    jQuery('#calculation-kriter3').html(kriter3);
    jQuery('.kriter3-aciklama').html('İş Günü Sonrası Tarih : ');
    jQuery('.kriter3-sonuc').html(kriter3);
  } 
  
  return [kriter3];
})();