I want to make a stacked column that has 4 variables, two of which are always
zero or positive and two which are always zero or negative. The four
together make a net sum. Excel seems to start my positive and negative sets
at zero and stack in both directions. The result is the column is taller
than it is supposed to be because it is not debited the negative values. How
can I change this so that my column is as tall as the net sum of the 4
values? For example:

A 5
B 8
C -2
D -7
Sum = 5+8-2-7 = 4

My column should be 4 tall, with a switch from A to B at -1, a switch from B
to C at -9, a switch from C to D at -11, and D ends at -18.