Filtering changes in dates and Avg grades
 

Hello,


I was wondering if anyone can help me with this problem. I have a 3
columns:
Student Names, Dates, and Grades and I'm trying to filter out a way where I
can capture the changes in each grade for each student every 5+ months. For
example:

Student Name Dates Avg Grade
Bill 1-01-06 80
Bill 2-5-06 80
Bill 8-10-06 75
Bill 2-22-07 90

From the example, I basically I want to capture from 2-5-06 and 8-10-06,
Bill's grade dropped from 80 to 75.

Thanks