INT MessageBoxF(HWND hWnd, LPCSTR szFormat, LPCSTR szCaption, UINT uType, ...)
{
        CHAR szBuffer[1024] = { 0 };

  va_list pArgList;

       va_start(pArgList, uType);
  vsnprintf_s(szBuffer, 1024, szFormat, pArgList);
    va_end (pArgList);

      return MessageBox(hWnd, szBuffer, szCaption, uType);
}
    

cproc MessageBoxF, hWnd, szFormat, szCaption, uType
local szBuffer[1024]:BYTE

lea eax, [uType+4]
stdcall vsnprintf_s, addr szBuffer, 1024, [szFormat], eax
stdcall MessageBox, [hWnd], addr szBuffer, [szCaption], [uType]
ret

endp    

proc MessageBoxF c, hWnd, szFormat, szCaption, uType

The class of printf functions (which stands for "print formatted")...

proc MessageBoxF c,hWnd,szFormat,szCaption,uType

        local szBuffer[1024]:BYTE

        lea eax,[uType+4]
        cinvoke _vsnprintf,addr szBuffer,1024,[szFormat],eax
        invoke MessageBox,[hWnd],addr szBuffer,[szCaption],[uType]
        ret
endp
    

I've rewritten in this way

I think that is right to use cinvoke for _vsnprintf and invoke for MessageBox.

There's a way to avoid using _vsnprintf and use macros ?

It must be "cproc", not stdcall "proc", because it is vararg.

proc MessageBoxF c,hWnd,szFormat,szCaption,uType

"c" after MessageBoxF doesn't make difference ?

proc Something c arg1,arg2