Hi,
you can easy achieve this with the normal combo like that:
<select id="cc2" style="width:150px"></select>
<div id="sp">
<div style="color:#99BBE8;background:#fafafa;padding:5px;">Select a language</div>
<input type="checkbox" name="lang" value="01"><span>Java</span><br/>
<input type="checkbox" name="lang" value="02"><span>C#</span><br/>
<input type="checkbox" name="lang" value="03"><span>Ruby</span><br/>
<input type="checkbox" name="lang" value="04"><span>Basic</span><br/>
<input type="checkbox" name="lang" value="05"><span>Fortran</span>
</div>
$('#cc2').combo({
required:true,
editable:false,
multiple:true
});
$('#sp').appendTo($('#cc2').combo('panel'));
$('#sp input').click(function(){
var my_text = '';
var my_val = '';
$('#sp input').each(function(){
if ($(this).is(":checked")) {
var v = $(this).val();
var s = $(this).next('span').text();
my_text == '' ? my_text = s : my_text += ','+s;
my_val == '' ? my_val = v : my_val += ','+v;
}
});
$('#cc2').combo('setValue', my_val).combo('setText', my_text);
});