Chalkboard - Writing Hand?

Hello,

I have an interesting idea floating in my head.  Do you have any ideas on how I could use an image of a chalkboard, and have a hand write letters on the chalkboard? 

For example....you land on a slide where there is a blank chalk board and a hand scrawls the letters on the chalkboard which moves as the letters are written.

What are your thoughts?

Thanks,

Dave