$result = dbquery("SELECT  * FROM ".$db_prefix."message_chronik WHERE (chronik_from='User1' AND chronik_to='User2') OR (chronik_from='User2' AND chronik_to='User1')  ORDER BY chronik_time ASC");

while ($data = dbarray($sql_query)) {

   if( $data['chronik_from'] == "User1") {

      echo "rechts";

   } else {

      echo "links";

   }

}