Gradebook

Hi-
I am really confused as to how best to set up what I want to do.

In my school, I am using forum discussions for pretty much anything that will be part of the students' grades. I have one forum per lesson in which they can talk with each other and help each other, and then one where they post writeups of their assignments. I have these forums set to "sum of ratings" for aggregate type.

I set up a grade scale of 0-4, with 4 being the best. I have some assignments turned in already which were great, so I gave them a 4. In the discussion forums, I had some students be very helpful to others, and although that's not an assignment, I would like to give those posts points that increase that student's grade.

The problem is that when I do give, say 2 points to a post by a student who had an earlier assignment they got a 4 on, their overall grade shows the average of their 2 grades, not the sum. It's expressed in a percentage, but basically, if they got a 4 on the assignment and a 2 for being helpful, their overall grade drops to a 3. What I want is for the 4 + 2 to give them a 6.

I thought sum would do this, but apparently not. Any tips on how to set up what I want?

Thanks!