Change profit center assignment in cost center

Hi All,

We have around 20 cost centers and assigned to 10 different profit centers.From 01/01/2011,we would like to change Profit center assignment in cost centers.

all cost centers postings should post to old profit centers till 12/31/2010 and from 01/01/2011,postings should go to new profit centers.

What is the best way to achieve this?any help is appreciated.

Thanks,

Anusha