How do I insert a new line in a excel spreadsheet without destroying the
consistency of the formulas?

Cut down to a minimum, the following is what I want.

Starting point:
B2=B1+A2
B3=B2+A3

Desired result after inserting a new line BETWEEN line 2 and line 3:
B2=B1+A2
B3=B2+A3
B4=B3+A4

I have been using SuperCalc for many years now, where this is a very simple
command. But I have newer been able to make the shift to excel. Just because
I could not figure out how to make this simple insert.
I have been trying at least four different types of relative referencing,
but they are all producing the wrong result:
B2=B1+A2
B3=<empty
B4=B2+A4