A Broadway tickets web service

  I want to buy tickets to a Broadway play this Saturday and/or Sunday.
  It's the height of the season, so the best plays are sold out.
  Yes I know about the TKTS booth in Times Square.
  What I want is a ticket-broker site that takes a query like the one in italics in the first line of this post.
  I know some of the shows have seats open. But so far all I can find is a hunt-and-peck interface. I can ask about individual performances of individual plays. That's going to take forever. A service like Hipmunk or Kayak for plays. Now that would be nice!
  If you know of such a service, helllp! If not, get busy. :-)
  PS: To be clear, all the services ask you to pick a play first, not a time. I only have certain times available. I want to know what plays I can buy tickets for at those times.
  PPS: In the VRM world envisioned by Doc Searls, I would write a blog post like this one, and the offers would start streaming in.