Limit CFrame Rotation? [Not Answered]

So this script makes a Part follow you're mouse. Thing is, I dont want the part to be turning to the mouse if it's pointing 180 degrees of that part. I would like to limit it like, 30 degrees to the left and right (Doesnt need to be exactly 30, just some number that limits the parts CFrame Rotation.)

local Player = Game.Players.LocalPlayer
local Mouse = Player:GetMouse()

while true do
local person = Player.Character
if person ~= nil then
local neck = Player.Character.ATST.Head.Neck
local looking = CFrame.new ( neck.Position, Mouse.Hit.p )
neck.Neck.C0 = neck.CFrame:toObjectSpace(looking)
end
wait()
end

Here's a simple function I wrote that limits a vector v to be within a certain angle (in radians) to vector d.

function coneLimit(v,d, angle)
	v , d = v.unit, d.unit;
	local dot = d:Dot(v)
	local toward = dot * d;
	local side = v - toward;
	local outtoward = math.max( math.cos( angle )  , dot) * d;
	local om = outtoward.magnitude;
	local sm = side.magnitude;
	-- (Q * sm)^2 + om ^ 2 = 1
	-- sqrt(1 - om^2) / sm = Q
	local Q = math.sqrt(1 - om^2) / sm;
	local outside = side * Q;
	return side * Q + outtoward;
end

Essentially, this constructs a triangle using two components: the component forward (in the direction of d) and the component to the side (side).

It restricts the forward to have to be forward by at least a certain amount (outtoward) and then sums that with a scaled side (by Q) to use the right proportion of each to make a unit vector.

A hypothetical use would be the following, to restrict a headlookvector to be within 30 degrees of a torsolookvector.

headlookvector = coneLimit( headlookvector, torsolookvector, math.rad(30) )