ASK: Adjust the automatic settings when you add a new row

hi everybody ..

I have a simple sheet to calculate the revenues and expenses and gross remaining in the treasury (balance) ..

But This sheet has a specified number of rows, and each time if i add a new row must I add the calculation for the row to get the total (balance).

How can I add a new row and takes the same calculation method of the previous row.? !!

In the sheet:

Columns are as follows:

A Date

B Discrption

C revenues

D expenses

E Balance

F Notes

Operations in rows as follows:

1 detection title

2 insert the date, Description and revenues only, and the balance is the same as the value entered in revenues.

3 insert the date, Description and revenues, or expenses , the balance 3 is as follows:

=SUM(balance2+revenues3-expenses3)

***

The problem I have is when you add a row 4 must Enter same calculation method of the previous to conform to row 4, and so on in each row is inserted.

MY ASK:

How can I make any add a new row to take automatically this process (the previous row balance+current revenues-current expenses) ..?

best regards,

yaser