The Negative Volume Disparity Indicator was created by Phillip C. Holt (Stocks & Commodities V. 14:6 (265-269)). This converts the classic Negative Volume indicator into Bollinger Bands and calculates the percentage of where the value lies within the Bollinger Bands. Buy when the nvdi rises above its signal line and sell when it falls below the signal line.
The OBVDI was a special request so I figured I would add this one as well. Let me know what other indicators you would like me to write scripts for!