Php – Zend_form_element_select onchange in zend framework

I have a form named createDevice.php as:

class Admin_Form_CreateDevice extends Zend_Form
{
public function init()
{
    $this->setName('Create Device Access');
    $sort=new Zend_Form_Element_Select('employee_name');
    $sort->setLabel('Employee Name:');
    $this->addElements(array($sort));
    /* Form Elements & Other Definitions Here ... */
}

}

Now In controller action named viewDeviceAction() I have called this form as:

public function viewDeviceAction()
{
    echo 'viewDevice: ';
    $form_device=new Admin_Form_CreateDevice();
    $form_device->setMethod('post');
    $form_device->employee_name->addMultiOptions($aMembers);//here $aMembers is an array.
    $this->view->form=$form_device;
 }

Now I want following situation:
On selecting any value from above dropdown a javascript function (which resides in viewDevice.phtml ) should be called.Like in general html as:

<select id="EmployeeId" onchange="loadDeviceId();">

So I just want to khow that how to implement the onchange event on the select element in zend framework