need authorization for business document services attachment list with user status in ps claim for clm2 and clm3

Dear Friends,

client wants to restrict the attachment list changing, deletion after the user status sets to close in PS Claims for transaction clm2 and clm3.

Currently any one can attach documents as GOS and delete even the claim is completed and status is closed.

How can we restrict all users even who created the claim can not change create and delete attachment list documents once the claim is completed and approved and user status sets to closed.