I suffer from excessive sweating..on my hands!?

I have the same problem, and have been faced with similar situations. Go to the party, even if the machine doesn't work. You can't let something like sweaty hands interfere with your life. While it may be incredibly embarring, I suggest telling the boy from the start that you have really sweaty hands. Although he may give you (in fact he probably will give you) a funny look, be prepared. If you can learn to live with it, others won't have a problem with it. I've found that even some of my closest friends make fun of my sweaty hands, but I just laugh with them. Be confident, don't worry, and just have fun at the party! Don't let a little dance get you down!