Formula to calculate cumulative balance

I'm new to using formulas in excel and what i'm trying to do is i'm sure rather simple but need some help to set up.

I have three columns. In one column is credit, second column is debit, and third column is balnce. how do i set up a formula so the balance column automatically updates when i type a number into either the credit or debit?

Assuming you have a starting balance, say in D1, then in C2:

=D1+A2-B2

in C3:

=C2+A3-B3

copied down.

where the first credit/debit is in A2 or B2