How to add class to Form Elements plugin [type-select]

Hi. Who use this plugin http://ckeditor.com/addon/forms ? This plug-in has a multiselect button. Anybody know, how add class or ID to select ? For example, from plugin we have: 

<select name="myname"><option value="123123123">123</option><option value="124124">213124</option></select>

and How add class or ID to this select box? For example: 

<select class="myclass" name="myname"><option value="123123123">123</option><option value="124124">213124</option></select>

or

<select id="myid" name="myname"><option value="123123123">123</option><option value="124124">213124</option></select>

Not at modal window. Adding this attributes by default. Example: I click on the button multi select list, add some values, and click Ok. After that at the source code I must see next: 

<select  id="myid" name="myname"><option value="123123123">123</option><option value="124124">213124</option></select>

Best regards. Thanks.

p.s. sorry, my English is not good.