I don't know why I never noticed this before..

The Dialog options in MESSAGEBOX() use a binary code 10 bits wide. (1, 2,....,512). There are many more possible combinations and the same effect could have been accomplished using a byte (the 4th and 8th bit aren't used). Therefore, I concluded that this must have been done for a reason.

Is there an undocumented way to utilize those bits?

Just wondering...