Format date Range on Cross Tab Report - Crystal Report 2008

Hi,

I have a cross tab organized by month in column. If the user enter the date  between 10/1/2014 to1/30/2014, the columns show:

10/1/2014  10/2/2014 10/31/2014 ......11/1/2014 11/2/2014 11/30/2014.

I need to format the dates as follow:

Oct 2014      Nov 2014

I have tried to right a  formula in "Column Options -> Group Options.. --> select tab Options --> check Customize Group Name Field --> Use a Formula as Group Name........ Obviously I am not able to do it.

Thanks for any help.

-Bill