Yikes! Don't do that. I thought you said you were scared?!? While it is incredibly daring to signal your attraction to a crush in front of the whole school, you risk embarrassing him and/or yourself. There's the possibility that he doesn't feel the same. If you're rejected, wouldn't you rather it be private? Even if he shares your feelings some people do not like being made the focus of attention like that. Also consider that if you're pointing to him in the audience, how do you know he'll be looking at you at the appointed time or that someone unintended will not mistakenly believe you pointed at them instead? Figure out a more private way to share your feelings, even if is telling him in advance that you selected the song with him in mind. Or afterwards wait for him to compliment you on how you did and then tell him. Good luck!