Calculate group subtotal in repeatable table with drop down menus

Afternoon all:

I have a dynamic form with an expanding table format. There are nine columns and one of them has a drop down list of six items, the last column is a value.

I need to subtotal the six dropdown menu items separately- preferably in FormCalc.

The grand Total works just fine. 

It seems like it should be easy enough, but I'm stumped. Any help would be appreciated.

Thanks!