Doug- I used to imleagues.com and then I changed to excel (using the imleagues availability calendar) and now I use the Arbiter. Arbitersports.com does have a fee to it, but it is easy to use and with officials on staff being certified and local assignors use that software it prevents me from scheduling students who have high school games and also prevents them from being assigned high school games if they are already assigned to work an IM contest. Feel free to contact me with questions.