before submit atleast one checkboxes is required

I have shown multiple check boxes,when I submit need atleast one checkbox is required., i tried this.,

$fieldset->addField('checkboxes', 'checkboxes', array(
            'label'     => Mage::helper('listings')->__('Select Categories'),
            'name'      => 'cat_ids[]',
            'values'    => $categorieslist,
            'onclick'   => "",
            'onchange'  => "",
            'value'  => $cat_ids,
            'disabled' => true,
            'class' => 'category_match_to_listing',
            'required' => true,
        ));

even class name also not displayed in html

<input type="checkbox" value="14" name="cat_ids[]" id="checkboxes_id">

if i use one values 'values' => 'single', required field working fine,then the html is

<input type="checkbox" value="0" class="category_match_to_listing required-entry" name="cat_ids[]" id="checkboxes_id">

when I get dynamic it doesn't work., please suggest any ideas?