Question

Is it possible to run a function every time a post is deleted. The function has to be run when the post is deleted from the admin or by the wp_delete_post() function.

Answer 1

Yep, http://codex.wordpress.org/Plugin_API/Action_Reference/delete_post

 add_action( 'delete_post', 'my_delete_function' );
 function my_delete_function() { 
   //delete some stuff
   global $post;
   print_r ( $post );
 }

Put that in functions.php of your theme and you’re set.

Read that link for any special circumstances you might need to account for