Is this a good way to ask a girl for her number?

Ok so theres girl in m cl that i Really liked and have liked since September. We talk a lot in school and i can tell her anything and she tells me everything too. It seems like we always have something to talk about and could talk for years. I want to ask her for her number but don't really know how. I think i have set up a perfect situation. So school just ended for the weekend.I know she never goes on facebook, so i sent her a message on facebook saying " I need to tell you something" Then on monday in school ill be like i needed to tell you something over the weekend but i couldnt cuz your never on facebook and i dont have your number, so just put it in my phone real quick. Then just hand her my phone. If she asks what i wanted to say ill just say i forgot. Is thiss a good way.