You are looking to create an Offset section. It will prompt you to make a sketch of the path the sectioning plane will take. This is not the same as a Planar section with an Offset Datum.
In the drawing you select the crosshatch and Properties. One of the choices is to Exclude the item from the section. You can either click Next/Previous until the section lights up on the item, or I think Select is available for you to pick it directly.
It won't change instantly; it will just not crosshatch it. You'll have update the view or repaint after you are done with the Properties.