How do I compute an average of calculated averages in MS reportviewer/rdlc? - reportviewer

Question

I've searched here and elsewhere on the web and have not found this exact problem/solution.
I'm building an rdlc report using the MS reportViewer - the report I'm creating is based on an existing spreadsheet where the average price across 6 months is calculated individually for each month, then the average of those prices is calculated as the 6 month period average price. Whether I agree with that methodology or if it's correct is irrelevant, I just need to know how to get an rdlc to do this.
For example:
Month Price1 Price2 Delta
May-12 $31.54 $30.03 $1.51
Jun-12 $36.27 $34.60 $1.67
Jul-12 $44.19 $42.00 $2.19
Aug-12 $38.96 $37.06 $1.90
Sep-12 $36.89 $35.08 $1.81
Oct-12 $35.57 $33.97 $1.60
Average $37.24 $35.46 $1.78
(sorry for the lack of a screen snip, I'm new and the system won't let me post an image...)
I've created a tablix that does the monthly averages computation - I use a group in the table to group the 6 months of data by month (and then hide the hourly price data so you only see the month total row) but I'm stuck on how to calculate the bottom row of the table which is the average of each column. (the average of the averages is not the same as the average of all 6 months of prices from the underlying data - that's what I've learned in this process... IOW, that was my first solution :-) )
What I tried to do to get the average of the averages was give the month total cell a name, MonthlyAvgPrice1, then in the bottom row, used this expression:
Avg(reportitems!MonthlyAvgPrice1.Value)
As I kind of expected, this didn't work, when I try to run the report, it gets a build error saying "The Value expression for the textrun 'Price1PeriodAvg.Paragraphs[0].TextRuns[0]' uses an aggregate function on a report item. Aggregate functions can be used only on report items contained in page headers and footers."
Hopfully I've explained this well, does anyone know how to do this?
Thanks!
-JayG

Answer 1

Actually it is not clear from the question that how are you in particular binding the data to the report items, But from the given information what I understand is that you can
Try like this:
Right Click the tablix row and insert a row below
In the cell where you want to have this Average of Averages insert the following expression
=Sum(Fields!Price1.Value)/6
and similarly insert expression =Sum(Fields!Price2.Value)/6 and =Sum(Fields!Delta.Value)/6 in the other cells where you want to display the Averages
Of Course, you will change the Field names Price1,Price2 etc to the fields that you are getting the values from.
HTH