Oscillator-development-issue-should-be-between-100-and-100

I have a small issue with an oscillator I developed by myself (in Tradingview). I wanted to transform it into WL8 but it does not work as planned.

The TimeSeries _ssmi should move between +100 and -100, but I only get a line that rises continously.

Maybe someone has an idea how I can realize this?

CODE:

    public class SSMI : IndicatorBase
    {
        public SSMI() : base()
        {
        }

        public SSMI(BarHistory barHistory, TimeSeries source, int highLowPeriod, int smoothingFactor) : base()
        {
            Parameters[0].Value = barHistory;
            Parameters[1].Value = source;
            Parameters[2].Value = highLowPeriod;
            Parameters[3].Value = smoothingFactor;
            Populate();
        }

        public static SSMI Series(BarHistory barHistory, TimeSeries source, int highLowPeriod, int smoothingFactor)
        {
            return new SSMI(barHistory, source, highLowPeriod, smoothingFactor);
        }

        protected override void GenerateParameters()
        {
            AddParameter("Bars", ParameterType.BarHistory, PriceComponent.Close);
            AddParameter("Source", ParameterType.TimeSeries, PriceComponent.Close);
            AddParameter("High/Low Period", ParameterType.Int32, 5);
            AddParameter("Smoothing Factor", ParameterType.Int32, 3);
        }

        public override string Name { get { return "Scaled Stochastic Momentum Index"; } }

        public override string Abbreviation { get { return "SSMI"; } }

        public override string HelpDescription { get { return ""; } }

        public override string PaneTag { get { return "SSMI"; } }

        public override PlotStyle DefaultPlotStyle { get { return PlotStyle.Line; } }

        public override WLColor DefaultColor { get { return WLColor.Green; } }

        public override void Populate()
        {
            BarHistory bars = Parameters[0].AsBarHistory;
            TimeSeries source = Parameters[1].AsTimeSeries;
            int highLowPeriod = Parameters[2].AsInt;
            int smoothingFactor = Parameters[3].AsInt;

            DateTimes = bars.DateTimes;

            if (bars.Count == 0 || bars.Count < highLowPeriod)
                return;

            TimeSeries hiLoDiff;
            TimeSeries relativeDiff = new TimeSeries(source.DateTimes);
            TimeSeries _ssmi = new TimeSeries(source.DateTimes);

            TimeSeries highestHigh = Highest.Series(bars.High, highLowPeriod);
            TimeSeries lowestLow = Lowest.Series(bars.Low, highLowPeriod);
            hiLoDiff = highestHigh - lowestLow;

            for (int bar = 1; bar < bars.Count; bar++)
            {
                relativeDiff = bars.Close[bar] - (highestHigh + lowestLow) / 2;
            }

            _ssmi = (EMA.Series(EMA.Series(relativeDiff, smoothingFactor), smoothingFactor)
                / (EMA.Series(EMA.Series(hiLoDiff, smoothingFactor), smoothingFactor) / 2) * 100);

            Values = _ssmi.Values;

        }
    }