Select Month range.-URGENT

[Sep2013]

Hi, I am using a dimentional data source which has a dimension of name period.
Following is the data in the period dimension:
2009-10
Jul 2009
Aug 2009
Sep 2009
Oct 2009
Nov 2009
Dec 2009
Jan 2010
Feb 2010
Mar 2010
Apr 2010
May 2010
Jun 2010

Similarly, same data exists for all the years, and the user wants the report to always show 6 months data back from today and 4 months data forward that is if current month is July2013, the user wantes to see data from january 2013 to November 2013.

Please suggest me a way to achieve this in cognos 10 report studio.