total (currentMeasure within set within crosstab rows

[Cognos Talk]

Hello,
I need to combine two quesry subjects into one but it gives me an error, it is a crosstab report , curently two calculation displayed oin two separate rows at the bottom of the crosstab, but i nee to unite them in to one row gainst 3 different colums

calculation 1

total (currentMeasure within set filter([Test Group], [Test Group] in ('Test1','Test')))
+
total (currentMeasure within set filter([Test Group], [Test Group] in ('Test2')))

calculation 2:

total (currentMeasure within set filter([Test Group], [Test Group] in ('Test2')))
-
total (currentMeasure within set filter([Test Group], [Test Group] in ('Test1','Test')))

how i can combine them into one row , it seems case function is not working well in the crosstab  row

i tried union but it was extrenmely slow and it does not work with hierarhical data model
thank you,
mila