static extern bool SetupDiClassGuidsFromName(string ClassName, ref Guid ClassGuidArray1stItem, UInt32 ClassGuidArraySize, out UInt32 RequiredSize);

    Private Shared Function SetupDiClassGuidsFromName( _

    bool Status = SetupDiClassGuidsFromName("class name here", ref GuidArray[0], 1, out RequiredSize);

        SetupDiClassGuidsFromName("class name here", ref GuidArray[0], RequiredSize, out RequiredSize);

    intRtrn = SetupDiClassGuidsFromName(ClassName, ClassGuid, GuidSize, GuidReqtSize)

    intRtrn = SetupDiClassGuidsFromName(ClassName, ClassGuid, GuidSize, GuidReqtSize)