How can I sort on an expression column in SSRS 2008

Because of the nature of my report, we need to be able to sort on the % growth on orders between 2 periods.  This is done by placing a dynamic column in the scope of the Period column header, then putting the following expression into the column.  (Expression is shown at the end of this post)  
What this expression does is:
If p1 value is 0, then growth is  100%, if p2 value is 0, the growth is -100%, otherwise the growth
is (P2 - P1) / ABS(P1).

HERE IS THE PROBLEM.  When I try to sort by this column's expression I get an error which basically
says "If you use an aggregate function in the column, you cannot sort on the column".
This is such a basic report requirement - show % growth and sort by highest to lowest (or vice versa), I cannot believe Microsoft did not envision of a way to do this.  This is the most obvious way, but this is also not the first time the SSRS functionality and obvious solution have been a cross purposes.  Frankly Microsoft's PM team on SSRS really needs to get out into the field more and see how people are trying to use this tool.  I'm getting tired of fighting it.

Anyone know how this could be done?  If not, can anyone suggest an alternative tool?  
HERE IS THE Expression

= Iif( (Sum(Fields!Period_Dollars.Value)= 0 ), -1,
              IsNothing(Previous( Sum(Fields!Period_Dollars.Value),"Group1" )), 1,
              (iif(IsNothing( Code.GetGrowth( Sum(Fields!Period_Dollars.Value), Previous( Sum(Fields!Period_Dollars.Value),"Group1" ) ) ), 0,
              Code.GetGrowth( Sum(Fields!Period_Dollars.Value), Previous( Sum(Fields!Period_Dollars.Value),"Group1" ) ) ))
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Megan BrooksSQL Server ConsultantCommented:
People are using SSRS in a zillion different ways. Each new version addresses more and more of the primary needs, but I don't think it will never do everything that everyone wants it to do. You can provide feedback to the development team through
If you can use SSRS 2008 and precalculate the SUM() values, storing them in group variables then you might be able to remove all aggregates from the sort expression. Is that possible?
RandyVoltersAuthor Commented:
#1, yes I know about; however, the SQL Server team has no place to post general questions about released products; I was just there yesterday, the only thing currently open is the SQL Server 2008 R2 "watering hole"; which is of no interest to my company at all.

#2, yes, I could do all of the work - that defeats the purpose of a report generator doesn't it.  Therefore we are back to why use SSRS.  I understand your point, my point is that this is such a basic, often asked for report I cannot believe the developers didn't see the need to provide this ability.  Having done product management for software companies, it seems the SSRS team suffers somewhat from not being amongst enough 'real world' users.  All I ever hear in posts about problems with SSRS is "you're trying to get too much data", or "you could re-write your query" to basically work around the deficiency(s).

This is tantamount to admitting to the sin is it not?  "You're trying to get too much data" is a backhanded way of saying SSRS cannot scale out and perform; likewise any "You could re-write the query" is admitting that the criticism is valid and there is no answer.

Look, here's the deal - don't tout a feature as a work saver and then backpedal to 'You could do more work'.
I believe what you are telling me here is that, "No, Microsoft did not foresee the need to be able to sort on a column where the data is derived from an aggregate".  Which means the tool is useless for about 80% of all reporting needs?!??!  

I hope someone else has a better answer.

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