Sum a field Dynamicly

Oh so I've got this to work in a sense but not how I need it to work.

I have 3 databases:

1)List of Activities

2)Scheduling Database that uses a of activities generated from Database 1

3)A video logging database that also uses the activities list generated from Database 1

As of right now for summaries if you are in the Logging database there is a layout with a dropdown and you can chose a activity and it will tell you how many time that activity occurs in the logging database. The dropdown is a dynamically created list from the activates database.

What I would like is a list of all activities and then a sum for that activity. I know I am able to do this by creating a calculation and summary field for each activity but I don’t want to do this as the activity list can be added to or removed from on the fly.

What I would like to have is in my activity database a field for each activity that says Logging Sum _____ & Schedule Sum _____

Have a script or calculation that basically looks at the other database and checks to see how many times each activity appears. & it should get the name of the activity from the current database record.

EX/

Activity Name = Swim

Logging Sum = 2 (Checked Logging for amount of times "Swim" was present)

Scheduling Sum = 1 (Checked Scheduling for amount of times "Swim" was present)

Or if I am able to create a dynamic list separately in the Logging & Scheduling database that tells me how many times each activity appears. As I said it currently works with a drop down but that means I need to manually check each activity, which at the moment is 150+.

Any help would be greatly appreciated and I hope I made some sense and someone out there is able to understand me. :