[AndyD]

А тут, как раз таки, надо воспользоваться COMDispFunction

    Com sheet;
    Com Range;
    COMDispFunction f;
    str s;

    COMVariant varArg1 = new COMVariant();
    COMVariant varArg2 = new COMVariant();
    COMVariant varArg3 = new COMVariant();
    COMVariant varArg4 = new COMVariant();
    COMVariant varArg5 = COMVariant::createNoValue();
    COMVariant varRet  = new COMVariant(COMVariantInOut::OUT_RETVAL, ComVariantType::VT_ERROR);
;
    Range = sheet.range("D10:AK258");
    s = Range.Address(true, true, -4150);
    info(s);

    f  = new COMDispFunction(app, "ConvertFormula", ComDispContext::Method);
    varArg1.bStr(s);
    varArg2.int(-4150);
    varArg3.int(1);
    varArg4.int(1);
    f.call(varArg1, varArg2, varArg3, varArg4, varArg5, varRet);
    info(varRet.bStr());