Filtering averages on averages generated by the filtering - circular reference prob

Hi all, this is my first ever online post so go easy on me.

I have 3 columns, the first is the weight record, the second denotes the sheep and the day the weight was taken, and the third is the combined average of those weight records on that day, i.e. SheepDay! 'A10' has 2 records, with an average of 36.5 (kg).

My problem is: I need to filter column 1 (sheep weight) so that only weights within +/-10% of the previous filtered Day average (column 4 - no numbers available - the problem!) are kept. However, column 4 is generated from the filtered sheep weights, which rely on column 4 in the first place; hence we have circular reference.

Weight SheepDay! Day average Filtered Day average
56.50 A2 56.50
37.50 A5 37.50
35.50 A10 36.50
37.50 A10 36.50

Theoroetically I can do it one at a time, but # rows = 25000!

Is there anyway in which it can be done?

Cheers Dave

For forum.xlsx

Hi thanks for the reply. I have attached a file with the data and a small note trying to explain what I want to do.

If anyone has any ideas it would be much appreciated. I don't believe what I wish for is impossible.

Dave