code: private void addHiddenField(Panel form, String fieldName, String fieldValue) {
  
          Hidden inputField = new Hidden();
          inputField.setName(fieldName);
          inputField.setValue(fieldValue);
          form.add(inputField);
      }
docs: Creates a hidden input field with the given name and value and adds it to the form panel.<p>
  
  @param form the form panel
  @param fieldName the field name
  @param fieldValue the field value