Changing of account assignment elements in BCS Migration

Hi,

Now FM Former Budgeting is implemented in current system, we are going to migrate to FM BCS, But we want to have New Account Assignment Elements to be assigned to Old Account Assignment Elements in BCS afer Migration. And we will not continue to use old one.

Using the 110 Profile - Payment Budget.

Eg:

Purchase Budget uploaded is  F1+FC1+CI1 - 10000 $

Reservation created and consumption is 5000$

Available budget is 5000$

Now After Migration new budget is to be Assigned to new Account Assignment Elements F1+FC1+CI2 in BCS.

Can Anybody help on this Please....

Thanks in Advance.

SAM....