You can create your custom button in a function and hook it into post_submitbox_misc_actions
and this will add it right above the publish button.
To change the status use wp_update_post in an Ajax function. Give it a try and post back with your code if you run into any problems.
UPDATE:
add_action('post_submitbox_misc_actions', 'send_for_correction_button');
function send_for_correction_button()
{
//global $post;
echo '<div id="send-for-correction" class="misc-pub-section"
style="border-top-style:solid; border-top-width:1px; border-top-color:#EEEEEE; border-bottom-width:0px;">
<input id="save-post2" class="button button-highlighted"
type="submit" value="Send for correction" name="save">
</div>';
}
add_filter( 'wp_insert_post_data' , 'my_filter_handler' , '99', 2 );
function my_filter_handler( $data , $postarr )
{
if ($postarr['save'] == 'Send for correction')
$data['post_status'] = 'on-correction';
return $data;
}