We all know that the value of an Bank Nifty is derived from top banking sector underlying stocks.
The value of Bank Nifty is calculated from free float market capitalization.
Using the same formula, I made an indicator on the bases of weighted volume of each stock.
This indicator will help you to plot Volume on Bank Nifty.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.