Run Magento Cron programatically

<?php
define('MAGENTO_ROOT', getcwd());
$mageFilename = MAGENTO_ROOT . '/app/Mage.php';
require_once $mageFilename;
Mage::setIsDeveloperMode(true);
ini_set('display_errors', 1);
Mage::app();

echo "Begining...."."\n";
try{
$observer = Mage::getModel("ism_import/cron_stock");
$vall = $observer->importStock();
print_r($vall);
}catch(Exception $e)
{
  echo "An exception occured.".$e->getMessage();      
}
echo "Ending...."."\n";