How to handle opening balance in new sub consolidation

I try to create a new sub consolidation.

Original structure

A

|------A1

|------B1

|------B2

New structure

A

|------A1

|------B

|----B1

|----B2

After consolidation, the "B" new sub consolidation will missing all the opening due to only movement is consolidated.

However, most of the opening can be aggerated by B1 and B2. Anyway to calculated the opening balance instead of manual adjust by input data at opening adjustment?