code: private void initResetCheckbox(CheckBox box, final CmsDateField field) {
  
          box.addValueChangeListener(new ValueChangeListener() {
  
              private static final long serialVersionUID = 1L;
  
              public void valueChange(ValueChangeEvent event) {
  
                  Boolean value = (Boolean)(event.getProperty().getValue());
                  if (value.booleanValue()) {
                      field.clear();
                      field.setEnabled(false);
                  } else {
                      field.setEnabled(true);
                  }
              }
          });
      }
docs: Creates a reset checkbox which can enable / disable a date field.<p>
  
  @param box the check box
  @param field the date field