I need help retrieving the last (Max Date) certification records from my training app.

I need help retrieving the last (Max Date) certification records from my training app. The Parent table is ?Employees?, the Child table is ?Training/Certification?, and each employee can have multiple records. Certification is required every 30 days, but training/re-training or practice can occur multiple times during the 30-day period. I could not get any of the suggestions I found in the Online Help or Community to work. Ultimately, I want to create a notification/subscription, based on the last date of certification, of the due date of re-certification.