Idea behind return codes in wxMessageBox?

[Anonymous Remailer]

Does anyone know what the idea is behind the wxMessageBox function
returning codes like wxYES /wxNO / wxCANCEL instead of wxID_YES /
wxID_NO / wxID_CANCEL? This makes it harder to use if you use it in
combination with another dialog box (say, one where you ask if the user
wants to save) and use a global variable for both return values. Since
the return values are incompatible you need to translate the wxYES to
wxID_YES etc. I find this cumbersome and unnecessary but maybe I'm
missing something obvious.

[Fritz Wuehler]