Crystal Reports Standard Devoation for multiple sets in one report

Message

I've got a report that is trying to show 2 different things..

 1.) a set of units sold from the day the report is run for the last 365 days sorted by part ID's.  This is not the problem

 2.) within the set defined in #1, the units sold in a "window" of time.
  Say, the first 2 weeks and the last 2 weeks of the data out of #1  
Again, using the sorted by part ID's.  

 Getting the sum of 
units sold out of these for each part is not the problem.  The problem 
is, I need to figure standard deviation on each part for both #1 and #2.
  #1 isn't hard to do, but trying to figure out how to do the average 
and other related calcs to get the standard deviation for the data in 
the window, seems to be a bit hard to do.... any ideas?

Edited by Beaker74 - 21 May 2012 at 5:02am