You can create a global function messagebox and edit the source to include all possible options. See below.

global type messagebox from function_object
end type

forward prototypes
global function integer messagebox (string as_title, string as_text, icon aico_icon, button abut_button, integer ai_default)
global function integer messagebox (string as_title, string as_text, icon aico_icon, button abut_button)
global function integer messagebox (string as_title, string as_text, icon aico_icon)
global function integer messagebox (string as_title, string as_text)
end prototypes

global function integer messagebox (string as_title, string as_text, icon aico_icon, button abut_button, integer ai_default);

// code do display window goes here 

end function

global function integer messagebox (string as_title, string as_text, icon aico_icon, button abut_button)
return messagebox( as_Title, as_Text, aico_icon, abut_button, 1 )
end function

global function integer messagebox (string as_title, string as_text, icon aico_icon)
return messagebox( as_Title, as_Text, aico_icon, OK!, 1 )
end function

global function integer messagebox (string as_title, string as_text)
return messagebox( as_Title, as_Text, Information!, OK!, 1 )
end function