in case you __should__ need any help,you cancall me by this phone number为什么不能用would?

In case you should need any help, you can call me by this phone number.
在in case引导的目的状语从句中,会用“should+动词原形”的结构,但should可以省略,在此处in case是以防万一的意思,也就是说“一旦你需要帮助,你可以打我这电话”,所以这里只能用should,或者省略,加should只是一种语气,无实义.如果用了would,那就不能构成目的状语从句,成了虚拟语气的话,就是与过去事实相反了,这显然不对的.所以你应该是把这两者搞混了,这里的should不是虚拟语境下的should,要注意辨别.非常感谢，you are good at English,thank you very much