Arsalan: Thank you!

Yes it requires to have a cron job to be written.

<?php
define('OSSN_ALLOW_SYSTEM_START', TRUE);
require_once('system/start.php'); //change to full path to system/start.php file

function delete_2weeks_posts(){
	$wall = new OssnWall;
	$listUser = $wall->GetPosts(array(
			'page_limit' => false,
			'wheres' => array(
					"(FROM_UNIXTIME(o.time_created) >= DATE_SUB(NOW(), INTERVAL 2 WEEK))"				  
			);
	));
	if($listUser){
		foreach($listUser as $post){
			$post->deleteObject($post->guid);
			ossn_trigger_callback('post', 'delete', $post->guid);	
		}
	}
}
delete_2weeks_posts();