Passing optional arguments to a COM function in VC++

CComVariant vFalse = false;
CApplication application;

{
    application.CreateDispatch(_T("Word.Application"));

    CDocuments documents = application.get_Documents();

    CComVariant vFilename = _T("c:\temp\test.rtf");
    CComVariant vNothing;
    CComVariant vEmpty = _T("");
    CComVariant vOpenFormat = 0;
    application.put_Visible(TRUE);

    //
    // THIS FUNCTION has a number of optional arguments
    //
    LPDISPATCH pDocument = documents.Open(&vFilename, &vFalse, &vFalse, &vFalse, &vEmpty, &vEmpty, &vFalse, &vEmpty, &vEmpty, &vOpenFormat, &vOpenFormat, &vFalse, &vFalse, &vOpenFormat, &vFalse, &vFalse);
}
application.Quit(&vFalse, NULL, NULL);

CComVariant vtOptional;
vtOptional.vt = VT_ERROR;
vtOptional.scode = DISP_E_PARAMNOTFOUND;

_variant_t vtEmpty(VT_EMPTY);