Sorry,
The possible way to go is
1)Modify the file modules/Froogle/config.php and add a new cron task
$cron_tasks[] = array(
'function' => 'func_froogle_cron_update',
'include' => $xcart_dir . '/modules/Froogle/func.php',
);
2)Add the function func_froogle_cron_update
The function should include the file modules/Froogle/froogle.php and emulate a regular POST request to create a new feed file.
3) Setup a new cron job according to
https://help.x-cart.com/index.php?title=X-Cart:Cron.php_-_Script_for_Periodic_Tasks
Meanwhile, the feature is added in X-Cart 4.7.10