Why does this not work?

I'm not sure why its not working, i'm trying to make it so when you're close to distance it gives you a force shield and when you're not close to the distance it removes your force shield..

distance = 50


while true do
	for i,v in pairs(game.Players:GetChildren()) do
		human = v.Character:FindFirstChild("Torso")
		if human ~= nil and (script.Parent.Position - human.Position).magnitude <= distance then
			while (script.Parent.Position - human.Position).magnitude <= distance do
				script.Parent.BrickColor = BrickColor.new("Bright red")
				local Check = v.Character:FindFirstChild('ForceField')
				Check:Destroy()
				wait(0.04)
			end
			wait(0.04)
			local ForceField = Instance.new('ForceField', v.Character)
			script.Parent.BrickColor = BrickColor.new("Bright green")
		end
		wait(0.04)
	end
	wait(0.04)
end