Auto Summary for Microsoft Dynamics CRM

http://www.gapconsulting.co.uk/solutions/essentials/auto-summary

“Auto Summary solution provides you with the ability to store information on a parent record summarised from multiple child records. With Auto Summary for Dynamics CRM 2011 you can sum any source field on all related child records and store the result on the parent record. It’s also possible to count the number of related child records and even apply a filter query before storing the result in the chosen field of the parent record. “