Get Mouse Location With Respect to any Camera/Object

Hi,
Am Currently working on a VR Project (First Person Shooter) where the Player can shoot any where on the screen. Am using Scene Capture to Texture method. The VR part is working fine. The Problem am facing is converting Mouse location to world space w.r.t My First Person Shooter Coordinates, the mouse location values w.r.t orthographic camera for rendering the Screen cast planes but i want to get w.r.t First person shooter coordinates. Is there any way that i can convert this values to my FPS axis or is there any inbulit function/blueprint to register mouse inputs w.r.t particular camera.