Using average function

[KezzerN]

I would be extremely grateful if anyone can help me with this problem: I select data using the filter option and work out the average of that selection. I then want to make another selection using the filter option and work out the average for the new selection. When I do this the original average I have worked out disappears as soon as I start selecting my new options via the filter. How can I stop this happening. Many thanks for your help.