Using a Workflow to remove unreceived items from a Return Authorization

We have return authorizations and sometimes the customer does not return all the items they said they would. Is there a way to use a workflow to find those return authorizations that are partially received and remove the items and the quantities if they were not all received to close the RA? Does this have to be done manually, or by a script only?

I do not see a 'remove item' on the workflow action items.