Translated from Russian by MetaQuotes Software Corp.
Original code: https://www.mql5.com/ru/code/10425
This script reads your unread GMail messages.Welch Bollinger Band ® Width
This uses the standard Bollinger Band calculations to further calculate the width of the Upper and Lower Bands, comparing that number to the Max and Min width of the bands for the last N periods. The results are plotted onto a histogram.