Without knowing exactly what is in which column it's a bit difficult.
Let's say they have positive or negative amounts going into column C, with an initial balance in C1. In D1 enter the formula
Hover the cursor over the bottom right of cell D1 and the pointer will turn into a +
Click and hold down the left mouse button and pull the mouse down to copy the formula down as far as you want.
If you then look in D2 the formula will be =SUM($C$1:$C2), in D5 it will be =SUM($C$1:$C5) and so on; i.e. a running total.