Trying to make a custom mouse lock feature, I need some help?

I am trying to make my own custom mouse lock feature, so when you click LCtrl it will toggle it. But it displays a error.

Error: "16:55:54.662 - Players.iiLevelMaker.PlayerGui.LocalScript:8: attempt to call field 'MouseLockSwitch' (a userdata value)"

Script:

local UIS = game:GetService('UserInputService')
local isShiftlock = false

UIS.InputBegan:connect(function(input)
    if input.KeyCode == Enum.KeyCode.LeftControl then -- When clicking LCtrl it toggles it
        if isShiftlock == false then
            isShiftlock = true
            UserSettings():GetService("UserGameSettings").CameraMode = Enum.ControlMode.MouseLockSwitch() -- Toggles it on
        elseif isShiftlock == true then
            isShiftlock = false
            UserSettings():GetService("UserGameSettings").CameraMode = Enum.ControlMode.MouseLockSwitch() -- Toggles it off
        end
    end
end)

But Idk how to use the MouseLockSwitch() feature and I tried looking up everywhere in the roblox wiki and searched on google but there's not tutorial on how to do it. It just shows this: http://wiki.roblox.com/index.php?title=API:Class/UserGameSettings/ControlMode & http://wiki.roblox.com/index.php?title=API:Enum/ControlMode

Could anyone please help, I would love it ;)