关于jquery怎样实现以下功能

自己生成右边的结构

 <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.min.js"></script>
<table>
    <tr><td valign="top">收件人：<input type="text" id="txt" style="width:500px" /><input type="hidden" id="txtIds" name="ids" /><br />
        主题：....</td><td id="tdContact">通讯录<br />
<input type="checkbox" class="all" />全部<br />
<div><input type="checkbox" class="sub" />交通局<a href="#">↓</a></div>
<div style="display:none">
<input type="checkbox" value="1" />交通局1
<br /><input type="checkbox" value="2" />交通局2
<br /><input type="checkbox" value="3" />交通局3</div>
<div><input type="checkbox" class="sub" />xx区<a href="#">↓</a></div>
<div style="display:none">
<input type="checkbox" value="1" />xx区1
<br /><input type="checkbox" value="2" />xx区2
<br /><input type="checkbox" value="3" />xx区3</div>
        </td></tr>
</table>
<script>
    $('#tdContact a').click(function () {
        var ex = this.innerHTML == '↓';
        this.innerHTML = ex ? '↑' : '↓';
        $(this).parent().next()[ex ? 'show' : 'hide']();
        return false
    });
    $('#tdContact input').click(function () {
        var all = this.className == 'all', sub = this.className == 'sub',checked=this.checked;
        if (all) $('#tdContact input').prop('checked', checked);
        else if (sub) $(this).parent().next().find('input').prop('checked', checked);
        var txt = '', ids = '';
        $('#tdContact input[value]:checked').each(function () { txt += ',' + this.nextSibling.data; ids += ',' + this.value; });
        $('#txt').val(txt.substring(1));
        $('#txtIds').val(ids.substring(1));
    });
</script>