=TRIMMEAN(IF(SUBTOTAL(3,OFFSET($C$3:$C$400,ROW($C$ 3:$C$400)-ROW($C$3),,1)),$C$3:$C$400),0.1)

where 0.1 is a percentage value.

The formula must be confirmed with control+shift+enter, not just with enter.

claytorm wrote:
Hi,

I want to apply TRIMEAN to a filtered data set. TRIMEAN ignores a set
percentage of outliers. I am currently using AVERAGE embedded in
SUBTOTAL, but there is no option to embed TRIMEAN within SUBTOTAL. Any
suggestions on how I could find a solution to this?

Bertie