How change an account to open item manage

We would like to change an account to open item manage but the problem is, it already has postings in it. We are using ecc 6.0

See error message issued by the system

You cannot change the open item management setting; (see long text)

Message no. FH087

Diagnosis

This account does not have a balance of zero.

System Response

You cannot switch the open item management specification on or off with this transaction.

Procedure

If you want to switch this function on retroactively for a certain account, you should create a new account with the correct setting and use this to make a transfer posting of existing items.

If you want to switch off the open item management function retroactively for an account, you must first clear all the postings currently on this account. You cannot make any changes to the account management method until this is done.