How to set 'Posting OK' indicator in MIRO automatic by default.

Hi Gurus

My client's requirement is like .....they want the 'Posting OK' (indicator :Invoice Item Processed) indicator to be automatically ticked in MIRO --> PO refernce screen so that user can not book invoice twice against the same PO item.

Any idea on how to set it automatic? Do we need to apply user exit for that?

Please Help.

Regards

Sanjib