This script measures the (default 20) Bollinger Band Width and draws a line. When the Bollinger Band compresses the indicator goes down and when it expands the indicator goes up. When the Bollinger Band Width compresses and expands to the lowest or highest degree for the last number of bars (default 200) it moves the Donchian lines to indicate the lowest and highest point for that period.
See the public release and Add to Favorites for access:
tradingview.com/script/Wruz221E-Bollinger-Bands-Width-Donchian/