Using 'Weighted mean of grades'

Case 2 - Using "Weighted Mean of Grades" to weight categories.

The first feature of the new grade book that I found myself wanting to be able to master is the ability to 'clump' assignments into categories and then have each category be assigned a different weight in the overall final grade. (Note - I'm avoiding the term aggregate to prevent confusion given the terminology used in the new grade book)

Example (how some classes are evaluated at my school)

Attendance & Participation 40% Quizzes 20% Tests (Mid-term & Final) 20% Final Projects 20%