title: How to set combo-box as default
body: <p>How to clear a combo-box selected values when clicking on a 'Clear' button? When the time of clicking clear button, it needs to set it as default. 
  I wrote it as;</p>
  
  <pre><code>DO:
      ASSIGN
      coCombo-2:SCREEN-VALUE IN FRAME {&amp;FRAME-NAME} = "".
      coCombo-3:SCREEN-VALUE IN FRAME {&amp;FRAME-NAME} = "".
  END.
  </code></pre>
  
  <p>"But this is not working."</p>