Christmas Party Scheduler

I love the holidays, I love the parties.  One problem I run into is getting just the right night picked out for the company party.  I need a program that I could have everyone in the office put in their previous engagements and then it would pick the best night for everyone to have the Christmas party on.  You could set certain parameters like no week nights or skip certain days totally.  You should also be able to set priority to the individuals going.  So if the program had two nights it could choose from and one night one of the main managers couldn't make it and the other night a guy who had only worked there for two months couldn't make it the program would schedule the party so the new guy missed the party (or vice versa depending on how great or horrible your parties are).