You've to specify all 3 caption replacements. The third one'll be ignored and can be an empty string

lnResult = EventMBox(version(1), ;
           MB_YESNO + MB_ICONEXCLAMATION, ;
           "EventMBox", ;
           "&Visual",   ;
           "&FoxPro", ;
           "")

>>>I recall a thread a while ago that discusses a way to use a messagebox and allow for changing the captions on the buttons to something other than ok/cancel or yes/no. However I can not locate it by searching. Does anyone know of a way to do this?
>>>
>>>TIA,
>>>Tracy
>>
>>See file #9676.
>
>Hi Sergey,
>
>Neil's example does work, but when I tried to use MB_YESNO instead it gave me Function argument value, type, or count is invalid (Error 11)
>A value passed to a function is either not of the expected data type, or the value of the argument is out of range for this function.
>
>
>You are passing too many arguments to a function.
>
>Here is my test. What is wrong?
>

>LOCAL lnResult
>#include foxpro.h
>lnResult = EventMBox(version(1), ;
>           MB_YESNO + MB_ICONEXCLAMATION, ;
>           "EventMBox", ;
>           "&Visual",   ;
>           "&FoxPro")
>
>if lnResult = IDYES
>	wait window "Wow!" nowait
>endif