Hello, I'm trying to use my Roku Streaming Stick to turn my TV into an extended display of my MacBook Air. I am able to set it up for mirroring no problem. However, when I try to use it as an extended display, the mouse only appears on the TV. I can't figure out how to make it move to the computer screen. I've tried moving it offscreen in every direction - up, down, left, right - no joy! Anyone have thoughts on this?