How to calculate average of row based on input in another cell

Question

I was wondering if you can show me a little trick here in Excel. I have a row here in Excel that is 25 columns wide as shown below.

What I want to be able to do here, is to calculate the average tonnage or kW annually. However I want to be able to input a number for the amount of years and for it to calculate that.

So in the image right now I have it set to calculate the average for 25 years. But let's say I want to average it for 20 years instead, so that I can input 20 into the years cell, and have the yearly average show up for the years of 1-20, rather than 1-25.

My macro skills aren't too sharp so any help is appreciated!

Answer 1

Use something like this:

=AVERAGE(C3:INDEX(C3:Q3,1,$C$11))

• where C3 - first cell of row with data
• C3:Q3 address of entire row
• C11 contains number of years to count (eg 10 or 20)

Answer 2

You don't need VBA for this. Try this formula out:
=IFERROR(AVERAGE(OFFSET(A1,0,0,1,A2)),"")
Where A1 contains the first data and A2 contains the number of years you want calculated.
Enter the formula in the Yearly Average column.