The On Balance Volume Reflex Indicator was developed by Fred Purifoy (Stocks & Commodities V 6:4 142-144) and it is similar in calculation to the On Balance Volume indicator but uses a lookback period for the change comparisons. Buy when the OVR is above the signal and sell when it falls below the signal.
I have included my On Balance Volume Modified Indicator to highlight the differences between both indicators.
Let me know if you would like to see me write scripts for more indicators!