How do I implement a Select All check box for Dojo v1.4.3 AdvancedDataGrid

I need to add a select all check box to the DataGrid checkbox column and code to programmatically check the boxes in the following jsp code

<%@page language="java" contentType="text/html; charset=ISO-8859-1"
      pageEncoding="ISO-8859-1" session="true"%>
<%@taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet"%>

<link rel="stylesheet" type="text/css"
 href="http://ajax.googleapis.com/ajax/libs/dojo/1.5/dijit/themes/claro/claro.css" />
<link rel="stylesheet" type="text/css"
 href="http://ajax.googleapis.com/ajax/libs/dojo/1.5/dojox/grid/resources/Grid.css" />
<link rel="stylesheet" type="text/css"
 href="http://ajax.googleapis.com/ajax/libs/dojo/1.5/dojox/grid/resources/claroGrid.css" />
<portlet:defineObjects/>
<script language="javascript" data-dojo-config="isDebug: true,parseOnLoad: true">

      dojo.require("dojox.grid.DataGrid");
      dojo.require("dojo.data.ItemFileWriteStore");
      dojo.require("dojox.grid.EnhancedGrid");
      dojo.require("dojox.grid.enhanced.plugins.IndirectSelection");
      dojo.require("dijit.form.Button");
      dojo.ready(init);

      var addPoliciesGrid;
      var addPoliciesStore;

      // set the layout structure:
      var addPoliciesLayout = [
      {
            field : 'policyNumber',
            name : 'Policy #',
            width : '70px'
      }, {
            field : 'billing',
            name : 'Billing',
            width : '90px'
      }, {
            field : 'owner',
            name : 'Owner',
            width : '80px'
      }, {
            field : 'insured',
            name : 'Insured',
            width : '80px'
      }, {
            field : 'paidTo',
            name : 'Paid to',
            width : '70px'
      }, {
            field : 'amount',
            name : 'Amount',
            width : '70px'
      } ];
      
      function init() {
            initalizeAddPoliciesStore();
      }
      
      function initalizeAddPoliciesStore() {      
            addPoliciesStore = new dojo.data.ItemFileWriteStore(
                        {
                              url : "http://localhost:10039/ProduceJSONWeb/servlet/com.mycompany.servlet.ReturnJson"
                        });

            addPoliciesGrid = new dojox.grid.EnhancedGrid({
                  id : 'addPoliciesGrid',
                  plugins: {indirectSelection: true},
                  query : {
                        policyNumber : '*'
                  },
                  store : addPoliciesStore,
                  structure : addPoliciesLayout
            }, 'addPoliciesGridTableId');

            addPoliciesGrid.startup();            
      }
      
      function displayAllCheckedPolicyNumber(){
      addPoliciesGrid.store.fetch({
          onComplete: function (items) {
               dojo.forEach(items, function (item, rowIndex){
                           if(addPoliciesGrid.selection.selected[rowIndex]){
                                 console.debug("rowIndex = "+rowIndex + " Policy # = "+item.policyNumber);
                           }
                     });
                     }                     
            });
      }
      
//http://dojotoolkit.org/reference-guide/dojox/grid/EnhancedGrid.html#dojox-grid-enhancedgrid
</script>

<div id="addPolicies" style="height:200px">
      <table id="addPoliciesGridTableId" dojotype="dojox.grid.DataGrid"></table>
</div>
<div id="showSelectedButton">
      <button onClick="displayAllCheckedPolicyNumber()">Show all checked Policy#</button>
</div>