justice41: the script would just tell you what braces it matches. You would compare what the script thinks with what you expect. It can't really tell which brace is mising.
Typically, it works like the one described above. You place the cursor over a open brace, hit a command key, and the cursor moves to the brace it thinks should close the open brace. With GUIs, the area between the open and closed is usually highlighted (appears selected).
If the selected area doesn't reach close brace you expected, you have an extra brace, and if it goes beyond the brace, you have a missing brace.