I had a need for a fully customizable MessageBox function that went beyond changing the text on the standard three buttons. Here's what I came up with. It should be documented well enough.
Thanks to Yashied and his Icons UDF. Parts are included (and attributed) in this UDF. Also thanks to trancexxx for her _StringSize function.
_MsgBoxCustom
#include-once
#include <WinAPI.au3>
#include <GuiMenu.au3>
#include <Constants.au3>
;~ #include <WindowsConstants.au3>