Cost Center in the existing legal entity

Hi All

From 1 of January 2016, one of the legal entity is going to start another branch, for that I need to create the new Financial Dimension “Business Unit” and from 1 January 2016 all the transactions should be done as per the business unit dimension.

 To achieve the above practice for this legal entity only I did the following (in test server) and stuck at one point:

1. Create the Financial Dimension
2. Create the Financial Dimension Sets
3. Create the new Business Unit in the Organization àBusiness Unit
4. Create the new account structure (Duplicate the existing) and add this Business Unit as the segment.
5. Remove the old account structure from the ledger form and add the newly created account structure where Business unit dimension is mandatory.

Till here it is fine for the new transactions that will start from 1 Jan 2016, but at the time of closing 2015 the opening balances should be transferred to the one business unit (old Business unit) with the business unit dimension so that when we generate the trail balance from 1 Jan 2016 onward based on the business unit I can see the all balances (opening) in the old unit.

So, I am stuck at last in closing, could you please suggest