Make an area Black and white

I want to have a Sphere that i can place that makes everything with in it black and white and possibly add other post process effects to the area. It should still be black and white from outside the sphere unlike the normal post process volume. Is this possible?

Check this out: 3D Modeling & Texturing: [Unreal Engine 4] Localized Post-Process Effects

Is this something that is applied as a blendable to a post process volume or as a translucent material on a box?