I am working on a chart for an aircraft charter service.  They have four airplanes that they maintain.  They would like to know the top 5 systems for each aircraft that require the most repairs and how much those systems have cost to repair. 

I think I need two On Change Of fields:

Registration
ATA-Code (This is the number assigned to each system)

and two Value fields
Count of ATA code (Top 5)
and Sum of Cost per write up.

Is this possible and if so how?