Last year we tried to figure out how people might be able to sell their Chometz over the Internet. Maybe you could pick up the mouse to make the kinyan, video yourself appointing the Rav to be your shliach and email the the resulting mpeg file. We're still looking into it.
In the meantime, you can print this Selling Chometz Contract, fill it out and bring it to Rabbi Welcher after Shacharis or Maariv.
