How do you change the history of a product sales account once you changed it to book into a new revenue account?

Thank you Rustler that helped me update my activities in the past. 

I'd like to add that the check mark option to update your historical transactions is shown only at the first time you switch the revenue account.  so if you forget to do it the first time, you can switch it to some other revenue account, save it and switch it back to the revenue account you actually needed to switch, then make sure to check the box this time.