Pinescript Volume Alert for Tradingview

Hi All
I'm sure this is a very simple script but I must be a very very simple person because I can't do it. I'm looking for an alert if the volume of a finished bar is more than double the volume of the average bar over a given period.

Can anyone help? I shall be ever in your debt and much Karma will come your way.

Thanks

MP

i see what can i do

Thanks. You are the greatest!