Title to be Changed by Custom Field?

Can I change the title by a combination of custom field values with the functions.php file? It would look something like this (I think):

$title = $number . ” ” . $first_name . ” ” . $last_name;
return title;

I have a custom post type, players, and I am hiding the title because I want the first and last names of the player separate. So I created a custom meta box. Is this possible to do so that it saves the title according to these three values and also changes the permalink?

Thanks.