Bollinger band percent (%B) as a function
BBPctF(expr, len, mult)
expr - data series formula
len - lookback period
mult - number of standard deviations
The BBPCT indicator always uses the series of closing prices for its calculations.
This function makes it possible to calculate the %B of any series of values.
This function supports ultra-fast one-pass calculation when used in the Data Section with a non-variable count.