You need to create different views, each one with a different filter applied to it.
You can also lock views to temporarily slow down creators from changing the filter. Creators can still unlock views and change filters, but it will slow them down for a moment.
Editors have more restrictions than creators, though, so editors won’t be able to change the filter on a locked view. So, if you give that employee editor-level privileges, he won’t be able to change the filter on a locked view.