Part only moves to the mouse once?

Ok so ive got a script so when u hold down q it would make a beam depending on where your mouse cursor is but i have a problem it only moves the mouse once then stops and doesnt move again how can i fix this?

local on = false
script.Remotes.On.OnServerEvent:Connect(function(plr,mouse)
    on = true
    local folder = Instance.new("Folder",workspace.Beams)
    folder.Name = plr.Name
    local endpart = Instance.new("Part",folder)
    endpart.Size = Vector3.new(0.99, 0.99, 0.99)
    endpart.Anchored = true
    local beam = script.Stuff.Beam:Clone()
    beam.Parent = plr.Character.LeftHand
    local att1 = Instance.new("Attachment",plr.Character.LeftHand)
    local att2 = Instance.new("Attachment",endpart)
    beam.Attachment0 = att1
    beam.Attachment1 = att2

    while on == true do
        local posx,posy,posz = mouse.X,mouse.Y,mouse.Z
        endpart.Position = Vector3.new(posx,posy,posz)
        wait()
    end
end)

script.Remotes.Off.OnServerEvent:Connect(function(plr)
    workspace.Beams[plr.Name]:Destroy()
    on = false
    plr.Character.LeftHand.Beam:Destroy()
    plr.Character.LeftHand.Attachment:Destroy()
end)