Customize my own post URL

Hi all, excuse my english, Im from spain... I have a question. I need to customize the Post URL. it's because I use my own URL system.

I have this code:

function set_post_content($entry, $form){
$post = get_post( $entry["post_id"] );
// Here I need to change or update submit URL
wp_update_post($post);
}

Anybody know how to do it?
Thanks!