A screen must be used in this exercise.
The screen must be that high and wide enough, that the CR is unable to see the helpers arms and by that the direction of the pass.

The helper stands with 2 balls.
The first ball is bounced softly to one of the sides and CR must react, when she sees the ball and catch it with the nearest hand.
At the same moment the first ball is caught the other ball is thrown softly and high to the other side, and CR must quickly move to that side after having caught the first ball (the movement to the other side is done right after the first ball is caught)