How To Add Stud Distance To A Script?

So here is a script that enables the player to click and drag a unioned part. What is necessary to add to this to make sure players are not able to drag the part from a certain distance?

plr = game.Players.LocalPlayer
mouse = plr:GetMouse()
target = {}

script.Parent = game.StarterPlayer.StarterPlayerScripts
function click()
    if mouse.Target then
        if mouse.Target:IsA("UnionOperation") and mouse.Target.Locked == false then
            target.part = mouse.Target
            target.anchored = target.part.Anchored
            target.part.Anchored = true
            dim = true
            mouse.Move:connect(function()

                if dim then
                    target.part.CFrame = CFrame.new(
                        mouse.Hit.X,target.part.CFrame.Y,mouse.Hit.Z)
                elseif not dim then
                end

            end
            )
            mouse.Button1Up:connect(function()
                dim = false
                 target.part.Anchored = target.anchored

            end)
        end
    end
end
mouse.Button1Down:connect(click)