Gentlemen,

MESSAGEBOX() is nothing more than a hook into the Windows API
function of the same name. The only difference between the functions is
that the FoxPro function doesn't require the window handle.

Actually, 16 (0-15) bits are used, 4 each for button configuration, icon, button focus and modality level. You won't find this well documented but there are three different modality levels. Not all of these bits, however, represent valid values. To answer the question, however, no it isn't programmable any further than setting the bits allows.

George