The reason for using OFFSET cell references is that it defeats the spreadsheets standard referencing behavior when new rows are inserted.

d3=d2+c3 will work to create a running balance. When a row is inserted Excel will repair all references to bridge around the inserted row. After the new info is entered in that row, the entire running balance column has to be repaired starting from the inserted row down.

d3=offset(d3,-1,0)+offset(d3,0,-1) will create the same running balance. When a new row is inserted, Excel will still fix all cell references, but since the cell only references itself, It still pulls values from the desired places. All that need to be done is to fill down into the new row, and edit the values as desired.

The downside to offsets is, sometimes, like when a column is inserted between c and d, Excel won't fix the references.

Thinking about that, in the second spreadsheet, maybe I should have used a combination, offset references for vertical, and relative references for the horizontal.
d3=offset(d3,-1,0)+b3-c3