How to update a cell when new data is entered

Hello, I needed help with something im working on.

I have a set data of data that counted average data of several years.

There is a column of average that i hid to help with the calculation.

Below my data which is a bar chart is a total for annual average

What I wanted was when i entered data in year 2015, the average for that year will turns out in that box.

And when I entered data for for 2016 it will updated to the new average in that box

Attached together is my work.

Any help is very much appreciated.

That is exactly what I wanted, and you modified it beautifully.

Thank you so much.