title: ExtJs 3 - Add listener
body: <p>I would like to accomplish:</p>
  
  <ul>
  <li>When some item in the ComboBox is selected hide some other field in the form or a complete div.</li>
  </ul>
  
  <p>This is my ComboBox:</p>
  
  <pre><code>var typeIDcombo = new Ext.form.ComboBox({
          fieldLabel: 'Type',
          name: 'typeid',
          store: typeIdData,
          displayField:'name',
          valueField: 'typeid',
          hiddenName: 'typeid',
          typeAhead: false,
          mode: 'local',
          triggerAction: 'all',
          emptyText:'Selecteer het type link',
          forceSelection: true,
          selectOnFocus:true,
          allowBlank: false,
          value: 'Selecteer een type',
      });
  </code></pre>
  
  <p>I have add listeners to my var form = new Ext.FormPanel. But this does not work.</p>
  
  <pre><code>listeners: [{
      'select' : function(field,nval,oval) {
       alert(field);
      }],
  </code></pre>
  
  <p>Does someone know a solution for this? Thanks in advance.</p>