Dress up or not dress up???

[RLC12345678]

Ok, so here's my delima. My hubby's boss, the head of surgery at the hospital, invited my hubby and me to his house on Friday for a "Halloween" Party. This surgeon plays in a band and his band will be playing at this party he's hosting on Friday. My hubby said it is a "Halloween" Party and I asked him if we are supposed to dress up and he said that he didn't know. None of our friends are going because we were the only ones invited, so it is not like we can ask them if they are dressing up in a costume or not. So what should I do? Dress up or not? I don't want to go to this big-time surgeon's house and be the only one not dressed up, but I also don't want to be the only one dressed up either! Ugh......men just don't know how to ask questions, do they!!!!