setting Non open GL item to Open Item

I have requirement to ch ange the gl master record from non open item manangement to open item managemt.as the GL having balances so it cant be done manually.

There's a programe available in sap RFSEPA02 which will support such requirement,but probelm is the SAP it self does not support to execute this programme and in my client system this programe is not executing.

How to make such GL as open item from Non open item which is having balances (almost 500 line items)?

Please guide me in steps for easy understanding.

Thanks,

Ranjan