Replace Summary column value with tuple expression

[bberryhill]

I have a reporting requirement to show measures for the last 12 months.  On most rows, the measure should be totaled but on the first and last rows the requirement is to show the value from the 1st month (for the first row) and the value from the 12th month (on the last row).
                                                  Month1  Month2 .... Month12   Summary
ProductDimension    Measure One        100        200          1200          100      <--- show value from month 1
                              Measure Two        400        400          400          1200      <--- show actual summary of the measure
                              Measure Three     900        800          700             700      <--- show value from month 12

I created data items to get the correction value:  tuple ( item ( [Last 12 Months Name],0 ) ,[Measure One] )
I set the summary cell for measure one, define contents to Yes.  Unlock the report and placed my data item in the cell.
When I run the report, the cell displays blank.  But, if I place my data item as another column at the end of the cross tab, the data is displayed correctly - so I know my data item / tuple is returning the correct results, I just can't get it to display in the correct place - in the summary column.

Any ideas, thoughts, solutions are greatly appreciated.
Cognos 10.2.2 -- Report Studio
The data source is a SQL server cube (SSAS).

Regards,
Bob