In my form view, I have a tree view for entries in a table (like sale order lines). When I add a new entry in the table, I want to populate fields in the new entry with data from the previous entry.

Here is an example. Suppose the column "Total" is a running total of expenses in the following table. Each time I add an entry into the table, I want "Total" to be updated with the value of "Expense" in the current entry plus the previous value of "Total".