You mean programatically? Could you be a little more specific? I guess the help you can get is limited to the size of the explanation of your problem.

// $AnyGroupObj is our group object.
if(elgg_get_logged_in_user_guid()==$AnyGroupObj->owner_guid)
{
    echo"..smile...;-)";
}

Thanks DhrupDeScoop

So i change my

mod\event_calendar\views\default\event_calendar\group_module.php

and add :

  if(elgg_get_logged_in_user_guid()==$AnyGroupObj->owner_guid){
        $new_link = elgg_view('output/url', array(
          'href' => "event_calendar/add/$group->guid",
          'text' => elgg_echo('event_calendar:new'),
        ));
    }

correct ?