You can do this by using a table along with the COUNTA function to discover how many records are in the table. You can then use the OFFSET function to extract the last 3 records.
You can see how to create a table in the video lesson: Expert Skills Lesson 1-11 Convert a range into a table and add a total row.
The COUNTA function and OFFSET functions are covered in the video tutorial: Expert Skills Lesson 4-6 Create dynamic formula-based range names using the OFFSET function.
The formula to calculate how many records are in the table will look like this:
To extract the last 3 records in the table, the formula becomes:
Now you can average the values by simply adding an AVERAGE function, creating the final formula:
I have attached a copy of your workbook with the formulas applied:
I hope this is the solution you were looking for, but please feel free to reply if you need any more help with this.
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