title: How can I change the choices in an OpenERP selection field based on other field values?
body: <p>I have a form with four fields:</p>
  
  <ul>
  <li>Crop - selection</li>
  <li>Active From - date</li>
  <li>Active To - date</li>
  <li>Block Area - selection</li>
  </ul>
  
  <p>How can I make the available options in Block Area depend on the values the user selects for the other fields?</p>