Well, I have figured out the "gross overhead" and "total expenses" embedded summaries. To illustrate, the embedded summary formula for the "gross overhead" would be:
GridValueAt(CurrentRowIndex,CurrentColumnIndex,0) +
GridValueAt(CurrentRowIndex,CurrentColumnIndex,1) +
GridValueAt(CurrentRowIndex,CurrentColumnIndex,2) +
GridValueAt(CurrentRowIndex,CurrentColumnIndex,3)
Now I just need to figure out how to sum up the rows in the embedded column on the right.