Help find the difference (delta) from the value returned from the last two records

I am using MS SQL 2005 and I created a CTE query to return values ​​from the last two records. I then use that to find the delta of two shapes. I have a working query, but I'm having problems getting nothing but a delta shape.

here is my request:

;with data as(
    SELECT 
        NetObjectID,
        RawStatus,
        RowID,
        rn 
    from(   
        SELECT 
            CustomPollerAssignmentID AS NetObjectID,
            RawStatus,
            RowID,
            row_number() over(order by DateTime desc)as rn 
        FROM CustomPollerStatistics_Detail 
        WHERE
            (CustomPollerAssignmentID='a87f531d-4842-4bb3-9d68-7fd118004356')
    ) x where rn<=2
)
SELECT 
    case when 
        max(case rn when 1 then RawStatus end) > max(case rn when 2 then RawStatus end) 
    then 
        max(case rn when 1 then RawStatus end) - max(case rn when 2 then RawStatus end) 
    else 
        max(case rn when 2 then RawStatus end) - max(case rn when 1 then RawStatus end) 
    end as Delta
from data having 
(SELECT 
    case when 
        max(case rn when 1 then RawStatus end) > max(case rn when 2 then RawStatus end) 
    then 
        max(case rn when 1 then RawStatus end) - max(case rn when 2 then RawStatus end) 
    else 
        max(case rn when 2 then RawStatus end) - max(case rn when 1 then RawStatus end) 
    end
from data) >= 1

      

        
        
        
      

    

What I need is to return Delta and NetObjectID. Every time I try, I get errors. data.NetObjectID is invalid in the select list because it is not contained in either an aggregate function or the group by clause.

If I try to add a group, etc., at the end of the request, I get an additional error, complaining about the word "group".

I am relatively new to SQL and I pick things up as I go. Any help would be greatly appreciated.