User Tom Gamon has discovered a clever way to sum up a time series, restarting at the beginning of each day. He uses the DayVolume indicator which is found in the Intraday Basic category. This indicator is designed to sum the volumes on each bar, but you can change the Time Series parameter from Volume to anything else. Note that the DayVolume indicator only exists in the NeuroShell DayTrader Professional.
Note that you can use the DayHigh and DayLow indicators similarly to find the highest or lowest value of some time series during the day.