Sage 100 Contractor: On current GL ledger account, want to be able to add subaccount/department without having to set up a new GL account#

On GL ledger account, we would like to be able to add subaccount/department without having to set up a new GL account # because there has already been activity posted to the account. This would prevent adding a new GL account and having to make an adjusting journal entry to move the existing balance from the old account to the new account.