[AtlUmpSteve]

I believe you are looking for this 2013 NFHS case play interpretation:

SITUATION 1: The pitcher, while standing on the pitcher's plate taking her signal from the catcher, tosses the ball back and forth between her glove and pitching hand several times. Once she receives the signal, she then brings her hands together and pitches the ball

RULING: The ball must remain in one hand or the other while the pitcher takes or simulates taking the signal. If she is tossing the ball back and forth from one hand to the other while taking the signal, it would be considered an illegal pitch (for not taking the signal with the ball being held in one or the other). The illegal pitch would be called the first time the pitcher’s hands come together and then separate while tossing the ball back and forth.

COMMENT: If the pitcher flipped the ball back and forth between the hand and glove without actually bringing the hands together, then held the ball in the hand or glove while taking the signal and started the pitch, her actions would be legal. (6-1-1a,b)