Calculate Average Return for the month of January for the last 15 years

[AdriTOS]

Hi,

I would like to calculate the average percentage return (close price vs. open price) for the month of January for the last 15 years for a stock .

I want to show a label in the graph so that it shows that average return when I select a particular symbol. (this I know how to do it)

If possible, I would also like to do calculate the same average return % but for the first 15 days of the month. If we are in February, then the averge return of a particular stock from Feb 1 to Feb 15 for the last 15 years.

Thanks