Run custom commands at registration OR only allow registration through API

[playigl]

In a way I am using WHMCS as a CMS - more so piggy backing off the login system to allow seamless integration with the rest of my site functionalities.

 

I require data be injected into a 3rd party table upon client registration. I have managed to complete this successfully by utilizing the API. However users can still register through the default means. Can the default registration be disabled, or even better - is there somewhere I can tack in a function to run upo successful registration?

 

Thank you!