Group account number / Group Chart of Accounts

Hi all,

We have created a new group COA and have assigned it to the company COA.

(In a production environment) We have assigned the group COA number under the Group Account Number of the company COA.

There is already transaction data's posted to these GL accounts for the entire year.

1. How to update these transaction data's with the Group Account Number?

2. Is there any program available to make this updating?

Thanks in advance