Life as we know it...

What's wrong with me? Have I gone crazy? Suddenly I'm cooking...a lot. And not just cooking normal stuff like spaghetti but actually looking for recipes and trying them out. I MUST have gone nutty.
I'm thinking about trying this recipe out for D's birthday this coming Monday. He loves cheesecake and he loves lemon. And it's from the Kraft website so it couldn't be THAT hard, could it?

My only question is, just how much juice do you get from one lemon? Because I have a thing of lemon juice at home that I just bought for the last recipe I tried...I'd rather use more of that than have to go buy a lemon. Anybody know the answer to this???