Prevent user from re-visit approval form. SharePoint 2010 Workflow

Question

I created a custom Visual Studio Workflow. It works fine and is a simple approval workflow.

There is a Workflow Task associated to a dynamic user and the user musst approve or reject it.

The Problem is, that the approving user can still access the form after completing the task and make changes...

I use the built-in approval form: <Task0_FormURN>urn:schemas-microsoft-com:office:infopath:workflow:ReviewRouting-Review:1031</Task0_FormURN>

So, even if the Task is completed, the approver can change the approval status of the item.

How to prevent him from that?

Answer 1

Create a view of the form that displays when the approval status has been changed and the user is the approver. The view can contain nothing more than a simple label informing them that the item has been responded to already (giving them the response and any other pertinent information) and that it cannot be changed or giving them the steps needed to edit their response (such as contacting the SPF admin.).

Answer 2

My suggestion would be to change their permissions on that item to Read. Then they can no longer make changes to it. I'm not sure of any other solution.