Need Multiple Select in a form

Hello all  I am using Modzzz Listing module.  I am currently attempting to switch from Single Select(Drop Down) to Multiple Select (Checkboxes) inside of BxListingFormAdd.php so that a user can select multiple values rather than just one.  It also needs to show up in the database as Value 1, Value 2, Value 3 if they select those values. See the code below. Any help would be appreciated.  I know you are a busy individual.

'specialty' => array(
'type' => 'select',
'name' => 'specialty',
'listname' => 'Specialty',
'caption' => _t('_modzzz_listing_form_caption_specialty'),
'values' => $aSpecialtys,
'value' => $sSelSpecialty,
'required' => true, 
'db' => array (
'pass' => 'Xss', 
),
'display' => 'getPreListDisplay', 
),

While for Dolphin 8 the idea is the same for 7.

http://www.boonex.com/n/dolphin-8-form

checkbox_set was the answer. I appreciate the help geek_girl. Solved this problem in seconds.