TRIMMEAN

Thank you so much for this. It works! But of course, I tried it with about 150,000 rows of data, and, yep, it's quite slow! For small-ish datasets, it's OK, but even for medium-sized ones with an Intel Core I9 solid state drive Dell all-singing all-dancing desktop, it's too slow. So I resorted to manipulating my data with M, grouping the data and coming up with a  calculated column (in M) from which I could exclude the tops and tails with a simple CALCULATE measure in DAX. But thank you, thank you for this DAX measure ... lots of interesting stuff in there for my file of "useful hacks".