Divide any 12 months into group of 3 months

Hi,

I have a report where in my report fetches previous 12 months data. Previous means previous from current month. So if report is run in Feb-2014 it fetches data from Feb-2013 to Jan-2014.

Now, I need to divide this span of Months into group of 3 months. Like:

02/2013 - 04/2013

05/2013 - 07/2013

08/2013 - 10/2013

11/2013-  01/2014

How can it be achieved.. Any inputs please..

I am working on CR for Enterprise 4

Thanks..