How to create a simple formula

[ep2002]

So I've never done formulas before & I want to try it out.

I need the total amount for the job somewhere in the sheet (would it go at the top?) & then I add in all the expenses added (assume it's one expense per line), & then as they are added, a sub total will insert like they do in some banks for online banking.

Example -

$500

Expense 1 - $50


Sub Total - $450

Expense 2 - $50

Sub Total - $400

And so on.

I'm not really sure how it should look. I don't want it to look cheap.

Thanks

[xor]

Enter amounts in column C or D as from row 5 and downwards.