Kinect plane alignment

Hi everybody,
I’m trying recognize objects in front of my screen with a kinect, that’s my setup To get only the objects which are near to my screen I use the threshold node to clip the rest of the kinect depth map.
But the perspective isn’t correct so when I’m on the right side of my screen the virtual shadows are to much on the right side and when I’m on the left side they are to much left.
I have seen the perspective kinect node but I have no idea how to use it.

What’s the best way to achieve to goal of a plane which is aligned to the kinect and the projector?