Reporting Services :: Get SCCM Report Code To Return Just One Collection

I have SCCM 2012 R2. I'm working on a custom report, using MS SQL Server Report Builder. I have other custom reports that work fine....they prompt for a collection and return results just on that one collection. The problem with the one I'm working on now is that it runs fine except for that....it prompts for a collection, lets you choose one collection,returns the desired info on each line, but it returns all systems, not just the one collection you selected. IOW, I'm having trouble getting the "where" clause to work right.

Here is the code for a report that works (it returns the selected collection and counts the patches needed by each machine):

select
    CS.Name0,
      CS.UserName0,
      CS.ResourceID,
case
when (sum(case when UCS.status=2 then 1 else 0 end))>0 then ((cast(sum(case when UCS.status=2 then 1 else 0 end)as int)))

[code]....

Here is the code for the report that I'm having trouble with. What you see runs but it has none of the collection selection code I've tried since I haven't gotten it to work:

SELECT
 DISTINCT(CPU.SystemName0) AS [System Name],
 CPU.Manufacturer0 AS Manufacturer,
 CPU.Name0 AS Name,
 COUNT(CPU.ResourceID) AS [Number of CPUs],
 CPU.NumberOfCores0 AS [Number of Cores per CPU],
 
[Code] ....

get the collection selection code to work in the second (processor count) sample?