Reach NPC - wait as long as npc is not reachable

[Atari]

Hi. I have problem with buying potions in Farmine. On label "potions" bot is buying potions just when the NPC (Rabaz) is reachable. When Rabaz is not reachable, bot waiting for a few seconds and going away without shopping. How to fix it?
How to do that character will standing near the table as long as he have to reach npc?

	elseif (labelName == "potions") then
		Walker.Stop()
		print([[Shopping]])
		if (Self.ItemCount(ManaPot) < MaxMana) or (Self.ItemCount(HealthPot) < MaxHealth) then
			Self.SayToNpc({"hi", "flasks", "yes", "yes", "yes", "yes", "yes", "yes", "trade"}, 65)
			wait(2000)
			if (Self.ItemCount(ManaPot) < MaxMana) then
				BuyItems(ManaPot, MaxMana)
				wait(500)
				BuyItems(ManaPot, MaxMana)
				wait(500)
			end
			if (Self.ItemCount(HealthPot) < MaxHealth) then
				BuyItems(HealthPot, MaxHealth)
				wait(500)
			end
			wait(200, 500)
		end
		Walker.Start()