Narrowing Drop Down Box for all COA Values when Entering transaction

Hi,

We have a client requirement where the client wants to restrict the list of values for all the segments in COA. We have say 6 segments in COA. The selection of value in 2nd segment should determine the next and so on till 6th (last). The requirement is to narrow down the COA list of values for all segments. It can be out of any solution and they are open.

The cross validation rule will not solve the purpose as it will list all values and throw error when a wrong combination is selected.

Security Rule will not solve since we may have multiple users using same responsibility (example Purchase Requisition).