Field loses its value when using rwmb_before hook

Hi There,

I am trying to hide metabox fields based on user role. For that I am trying to use rwmb_before action. The code is pasted below.

The problem that I am getting is that I can remove the field for a specfic user role. However, the hidden field loses its saved value. How can I preserve the value while hiding the fields for specific roles?

add_action('rwmb_before' , 'ta_hide_metabox_fields', 10, 1);

function ta_hide_metabox_fields($object){
    print "<pre>";
    print_r($object->meta_box['fields']);
    print "</pre>";

    foreach ($object->meta_box['fields'] as $idx => $item){
 /*       print "<pre>";
        print_r($idx);
        print "</pre>";
        print "<pre>";
        print_r($item);
        print "</pre>";
*/
        if($item['id'] == 'specialty'){
            unset($object->meta_box['fields'][$idx]);
        }
    }
}

Thanks!