Many animals like to use the same spot and use that spot to check if any new animals have invaded their special territory. Its like a scrape area for deer.
What you MUST do first is to neutralize that spot by eliminating all the odors eminating from that area. Remember, dogs can smell 100 times better than you. So, you must not MASK the odor but eliminate it.
Try pine sol, try anything that will penetrate deep into the wood and cover the scent. Try sanding the spot and then sealing it with polyurethane to cover the scent. There is a chemical called "dog be gone" that I spray around my garden and it keeps my dogs way clear.
Sorry about the lack of sympthay of that other poster. That was no answer.