That Won't Work (おっかねえよー) is an energy wave used by Chi-Chi as a child. First, Chi-Chi places her index and middle fingers of both hands on the forehead circle of her helmet, where she charges green energy. Then, she shouts, "I'll burn you to a crisp!" and fires the green energy from her helmet in the form of a laser beam. The laser beam scans from left to right at her opponent, inflicting a great amount of damage.
Chi-Chi used this attack to destroy the remains of a T-Rex that was chasing her after she decapitated the large reptile with her helmet blade. When Yamcha appeared to congratulate her, Chi-Chi attempted to attack him with the "That Won't Work" helmet laser beam. However, Yamcha dodged the beam at the last second and punched Chi-Chi to the ground, knocking her out.