How to change the prefixed codes

Hello

how can we change the prefixed codes for

invoice Purchase orders Quotes

as we have more than one company we want to add the initials of our company to the beginning of the quote numbers but don't know how to do this, please advice how we can do this please

So this is what I am thinking

CGS In CGS PO CGS QU

and then in the other company

CGE In CGE PO CGE QU

I thought I found how to do this for invoices and purchases orders, but it did not work

please help - as we will get confused using the same reference for both compaines

many thanks

Lynette