>How can I set the font attributes of the message text in a MESSAGEBOX() call, either globally for an app or locally for one call? Can anyone give me some sample code?
>

It's done through the Windows Display configuration applet; it gets set globally as a part of the Appearance tab; select the Message box setting and the last line allows you to specify a font and font size. It's a global effect; many end-users will become extremely unhappy if you do this to them, since it will affect how every program works with message boxes.