Landmark Security

You would need to do this in the configuration console I think? Anyone know how to do this?

You'd first need to have a custom security role for your actors. You would need to specify a condition for determining whether or not a user is allowed to see it.
Is this for an approvals process? I've found the best way to segregate things for approvals is via Process User Tasks and Filters, then manage the filters and tasks for users or user groups.
Is the determining factor based on their role? For example, if they're a manager, they can see it? But if they're not a manager, they can't? This would be managed through security console.