dependent checkboxlist instead of dropdown

How to have dependent checkboxlist instead of dropdown

 <?php

                        $list=CHtml::listData(XyzMaster::model()->findAll(),'abc_id','abc_name');

                        echo $form->checkBoxList($model,'xyz', $list,

                        array(

                     //   'empty'=>'Please Select',

                        'ajax' => array(

                        'type'=>'POST', //request type

                        'url'=>CController::createUrl('site/cat'), //url to call.

                        'update'=>'#Details_abc', //selector to update

                        ))); 

                ?>





   <?php

                        //empty since it will be filled by the other dropdown

                        echo CHtml::checkBoxList('Details[abc]','abc', array(),array('empty'=>'Please Select','style'=>'width:120px;'));                

                ?>

I am getting the checkboxlist for xyz but I am not able to select any elements

Any Ideas?

Anyone?