Mouse position & camera rotation based on it

Hello, I’m trying to setup camera rotation based on mouse position on screen (x axis). I ve done some basic setup. Where I can click mid mouse to start rotation to the left or right. However I have a few problems. As I said this setup is very basic and I’m testing it in 1200+ resolution window, if I change resolution this setup wont work propely anymore because 640 ofcourse not a half of 1900+ resolution for example and so on. Its a first question - Which way is proper to do a mouse position check on the screen in my case? And second question is - Is it possible to check mouse position and change mouse rotation on the fly so that I don’t need to click twice on my mid mouse button to change the direction of rotation?