FORCE_SSL_ADMIN

I’m trying to make my admin section a bit more secure by using define(‘FORCE_SSL_ADMIN’, true);
I’ve put this line of code in my wp-config.php file fine. I understand that this then tells the browser to look for admin files under https.

My problem is this: my hosting company puts my ssl folder under a completely different domain. Is there an easy way to reroute FORCE_SSL_ADMIN to this domain rather than just https of my existing domain?