Adding up totals from every time this item is referred to on a connected board

I am hoping to use connected boards to track volunteer hours. We have a master list of volunteers, and a second board of activities. Each activity is one line, and we use a connected board to click in all the volunteers who came along to that activity. On the activity board this sums up simply activity time x number of volunteers = total volunteer hours.

We’re hoping to then go “back up the chain” so the volunteer board shows:
1 - the total number of hours on all activities that this volunteer attended
2 - the date of the last activity that this volunteer attended

Thank you very much!

I’m all sorted! I think I must have set up a one-way board connection. Making a new two-way connection from the main volunteer list to the activity board is working like a charm (and showing that Peet is our no1 volunteer in terms of hours put in!)