Range name?

[patrickthatcher]

In our current 3rd party reporting tool, users have the ability to pick a range of dates and give those dates a name. For example:
Date 8/2/2015 - 8/8/2015 Name = "TY"
Date 8/3/2014 - 8/9/2014 Name = "LY"

This would result with the report showing a column with TY and LY values.  If the user chooses, they can drop the date field beneath the header and can see the individual dates that make up the TY and LY headers.  I am trying to do something similar in cognos, but I cannot figure out how to do this correctly.  While I can get the header to display the values that the user enters if they use only 1 range, my data is duplicated if they use 2 ranges.  This makes sense the way the report is setup, but I cannot seem to nest the vaules correctly to achieve my desired result.
Any idea how I do this correctly?

I've attached a spreadsheet that shows the prompt and report layout.
Thanks in advance