I have a report which details the time it took to close incidents in the ServiceDesk system, with a row for each incident.  I have created an average for the time to close but now I have to exclude the top 10% and bottom 10% from the calculation so only the middle 80% are evaluated.  I can't see how this can be achieved using Top N and the only answer I can think of is to manually calculate the middle 80% and then put the relevant figures into the report selection.  Unfortunately this report will be run on demand by the team management, so that's not really a solution.