A summary field can compute an average.
There is also the aggregate function of the same name, Average(). It would require a related table if your values are in separate records as they should be, but the summary field does not.
Right. I did forget about that. :)
I was actually trying to just average the top 10 records -- the 10 largest values.
So, in that case, I should write a script that does the sort, goes to the top, and walks down the table and adds things up in a set variable. Then I can decide when I hit 10 records using the loop exit via calculation step and set a global field.
Does this approach sound good?
Sorry I wasn't more specific in my original posting.
It will produce the correct value. It might be possible to setup a filtered portal for the top 10 and use a one row summary portal filter with the same filter to show an average. Such a value is strictly for display, you can't use it in a calculation, but it would avoid having to loop through your records to compute the average each time.
Thanks Phil! :)