Intercept admin toolbar trash task

Hi,

I have 2 tables in back-end: country and region.

Region as a foreigh key of country so they can be link. However, when I delete a country, it doesn't delete the region that has that country.

I have looked a bit in the code to see if there was a controller for that task as to intercept the delete task as to launch a sql comment to clear region which has that country id. 

However, I haven't seen any control. Can someone help me with this.

Thanks