Rolling period values in KP06 layout

Hi Experts,

Good evening.

We would like to have rolling periods in the Cost centre planning layout ( KP06).

My layout should have 12 periods.

Means.. if i enter 09 , 2013.. system should display 09,2013 to 08 2014 ( 12 periods)

If i enter 03, 2013 in the selection screen .. it should allow me to plan 03,2013 till 02,2014 ( 12 periods).

I found that Formula variable works in those cases for Information system (or) is there any way of doing it ?

Can we use formula variables in the KP06 layout ?

Thanks in advance

Siva