What is the name of this manga?

The manga is about a girl who is in high school and plays tennis. She meets this young girl who is a witch who has a pocket-sized computer-like spell book. The main character girl helps the young witch to achieve her goals. Well, that's all i know about it but i read this manga a couple years back, and i can't recall what the manga is. It keeps on bugging me. Could ya help me?