Listen for clicks outside of unity application

Hi, I am building an overlay application for Windows using Unity. I want my overlay to listen for clicks, even when another window is in focus. As far as I experimented, Input.GetMouseButtonDown(0) and other Event KeyCodes only work while unity app is in focus. Soon as I click another window, it stops getting events. I know it does make sense, as recording clicks in another process is uncommon and unthrusted. Anyhow, does someone know of another way to listen for mouse input, with a Unity app running in background ? Maybe using user32.dll or another Windows library?