I'm trying to write a calculation to get the average of grades. There are 14 grades per semester per student. Here's what I have for the calculation for Average grade Semester 1; Average ( Semester 1; Grade ), but it doesn't seem to work. This is what I have for the calculation for Semester 1: (Lesson Number ≤ 14 ), and I have different ones for each semester up to 8 semesters. Semester 2 is: (Lesson Number > 14 ≤ 28). I would like to get the average of the first 14 grades, then for the next semester, the next 14, etc... not sure how to do it.