Is it possible to make an AI follow the player on a NavMesh inside a sphere on the player?

Hi all, so I am looking for a way to get my Follower style NPC to follow the player inside a sphere. I have the player with a cylinder as a child of the player, which has a NavMesh on it (NPCLayer), the NPC randomly runs around the player at the moment, but obviously if I move the character the NPC stays in the same place, because the NavMesh is baked. But what I want to do is put a NavMesh on the terrain (Walkable), but only allow the NPC to create new random positions inside the sphere around the player. Is this possible to do and what would I need to do it, I am not looking for the code to be written for me, just some pointers.

Thank you in advance for any help.

Joxer.