Assuming the following formula in E14:
E13 should have your beginning balance, which would be 0 (Excel assumes a blank is 0).
D14 should have the first number you want to add to the beginning balance, e.g. 10.
So. the number in e14 (e13+d14) should be 10.
Copying/pasting the formula into f15, it should read
So. E14 is 10, as calculated above; +d15 which is the next number you are adding, say 32. E15 should equal 42.
And it carries on down, incrementing as you go.
Make sense? Only one cup of coffee so far, so if it doesn't I will drink more and try to explain it better.