Employee Attendance Tracker- Rolling 90 Days

Hello

I am an Excel Novice and not good with formulas so I am hoping someone can help me. I am trying to create an attendance tracker that will sum up points for the current to previous 90 days. I put in a drop down of the offense and want it to populate the correct value, and then sum all offenses for the last 90 days in the rolling points cell. I hoping someone has done this before and its an easy fix. Thanks for any help you can provide.