C++ WIN32 RichEdit Control don't put stream

Question

I try to put datas to my RichEdit50W but it doesn't work. I really need help.

My function CreateRichEdit :

void CreateRichEdit(HWND hwndOwner, int x, int y, int width, int height, HINSTANCE hinst)
{
    LoadLibrary(TEXT("Msftedit.dll"));

    edittext = CreateWindowEx(0, TEXT("RICHEDIT50W"), TEXT("Type here"), ES_MULTILINE | WS_VISIBLE | WS_CHILD | WS_BORDER | WS_TABSTOP | ES_AUTOVSCROLL | WS_VSCROLL,
        x, y, width, height,
        hwndOwner, NULL, hinst, 0);

    char * bidule = "coucou c'est moi";
    EDITSTREAM es = { 0 };
    es.dwCookie = (DWORD_PTR)bidule;
    es.dwError = 0;
    es.pfnCallback = EditStreamInCallback;

    bool ok = false;
    if (SendMessage(edittext, EM_STREAMIN, SF_RTF, (LPARAM)&es) == 0) {
       ok = true;
    }
}

And in my function EditStreamInCallback, in my variable 'txt', I well get the text "coucou c'est moi". But after, when I try to write in pbBuff , I don't see the result in my rich textbox:

DWORD CALLBACK EditStreamInCallback(DWORD_PTR dwCookie, LPBYTE pbBuff, LONG cb, LONG * pcb)
{
   if (!cb)
      return (1);

   char * txt = (char *) dwCookie;

   int i;

   for (i = 0; i < 3; i++)
   {
       *(pbBuff + i) = 'a';
   }
   *(pbBuff + i) = '\0';
   *pcb = 3;

   return (0);
}

I absolutely need help ! Do you have any solution please ?

Thank you in advance