Including a value once in a summed SSRS group

Question

I have a data source which is pulling in event attendance information which looks like the following table.

Note that one booking can contain multiple attendees, causing

Answer 1

The version of SSRS is key here. In SSRS 2008R2, you can now nest aggregate functions:

So this would now be a valid expression:

=SUM(FIRST(Fields!BookingPrice.Value , "BookingGroupName") , "DateGroupName")

If you aren't yet on 2008R2 then you can do some tricks with embedded code to keep a running total: http://beyondrelational.com/blogs/jason/archive/2010/07/03/aggregate-of-an-aggregate-function-in-ssrs.aspx

The key here is that you add to the total in the embedded code once per group. Then retrieve the total and clear it out at the end of the group.