Hi,
I don't have Clarion 6, but with 5.5 there is a system property that allow you to overwrite the builtin message box. You can do what ever you want in your own message procedure.
SYSTEM{PROP:MessageHook} = Address(MyMessageProcedure)
SYSTEM{PROP:MessageHook} = 0
MyMessageProcedure PROCEDURE(STRING MsgText,<STRING Caption>,<STRING msgIcon>,<STRING Buttons>,UNSIGNED btnDefault=0,BOOL Style=FALSE)
etc...
Good luck.
Valery.