Simply use elseif's to keep going with the if/else chain you have here. So you'd have an
else if (isset($_POST['delete'])) block. Simply follow the same logic you have for the editing. You'll probably want to keep adding with the logic to the edit as well, otherwise the form only deals with one field modification.
You should look at prepared statements as well to protect the input from corrupting the SQL Structure. Looks like the SQLSrv package does not roll its own version of mysql_real_escape_string.