Sending a status change email via cron

Our Open Cart installation gets shipping status updates from a 3rd party platform.

I'm trying to either:

* trigger the status change via some url / parameter and send out the "You order has been shipped" email

or

* change the status at database level and then send out the email

I can see the email script in admin/model/sale/order.php but am not sure how to access these routines from an external script e.g running a cron job

Any ideas?

also interested in this functionality.