怎样在lua实现点按循环 再点按结束循环啊

这是我的代码 想实现按下侧键4开始循环 按下侧键5结束循环 但总是失败
function OnEvent(event, arg)
--OutputLogMessage("Event: "..event.." Arg: "..arg.."")
if (event == "MOUSE_BUTTON_PRESSED" and arg == 4) then
repeat
PressAndReleaseKey("1")
Sleep(5000)
until (event == "MOUSE_BUTTON_PRESSED" and arg == 5)
end
end
到底问题出在哪 全网搜半天了找不到答案 烦死我了