Charlie,
Don't let that stop ya!!! I've got the same problem. You can look into when the other schools in your area are having their psats and take it through another school. I've got psats the weekend of the invitational, and another high school is having them the weekend before that (unfortunately I'll be albacore fishing that weekend also, so I got to school number 3 which is on a Tuesday. Perfect.). Something to look into. I don't know how many other high schools are in your area, or if they work it the same way, but you might want to consider it.
-Brian