Calculate the total from multiple records in a related module?

Hello, I'm using Sugar Enterprise 9.1 (Cloud). I'm trying to create a calculated field that will give a cumulative total of a decimal field in a related module. 

Attendance (Customized from the Calls Module) is used to track attendance. Points are given for certain situations, no call no show is 2 points, unscheduled sick is 1 point, late is 0.5 point, etc. 

I created a custom module called Personnel with a field named Cumulative Points. Employees receive warnings at certain point levels, so I'd like to create workflows for when the cumulative total reached 2, 4, 6, 8, and 10 points, but I can't figure out how to calculate the total of all Points in related records in the Attendance module. I tried rollupsum, but I can't figure it out. All of the examples I have looked at are based on dates or other multiple criteria. I'm simply trying to get a cumulative total. Any help is greatly appreciated.