How to use GetBars as a 2nd TimeFrame Source for Indicators

Hi,

I want two indicators for two different time frames:

 protected override void OnStart()
        {
            _emaLow = Indicators.ExponentialMovingAverage(SourceSma, 9); //current timeframe 1HR

            var dataSeries = MarketData.GetBars(TimeFrame.Hour4, SymbolName);

            _emaHigh = Indicators.ExponentialMovingAverage(dataSeries , 9); //timeframe 4HR
        }

I was told to use GETBars but it is not a valid type to pass on the indicator.

Thanks