I need to customize the "post edit page", for a custom post_type, but to keep things simple let's say it's on the post_type post for now.
When the post status is published, I need to run a PHP script that fetches some data from my database, based on the post_id of the current post.
Where do I add this script??
add_meta_box(). This function is the key to add custom areas to the edit screen and inside this can you handle your custom requirements.