General Ledger account numbering systems

SOLVED

General Ledger accounts question:  We are changing our corporate structure to add 2 subsidiaries and want to change our GL account numbering system to accommodate this.  I understand that you can only change GL accounts at year end, prior to beginning a new year.  Does anyone have a chart of accounts numbering structure that incorporates 3 different entities that they would be willing to show me as a model ?  We want to be able to both have separate and combined balance sheet and P&L information.

I understand that departments and subsidiary gl accounts are mutually exclusive, so you can only use one or the other system.  I was wondering about expanding the numbering system with another two digits at the end to create one GL system with the last two digits signifying the subsidiary company.  Has anyone done this ? 

Thanks,  Susan