Charlie,
In addition to the broken Y axis, you can display data on two different
axis. Assume you have the following in the range A1:C5 :
Ser1 Ser2
a 5 50
b 4 68
c 7 86
d 6 94
Select the entire range and create a line chart. Select the lowest line on
the chart (Ser1) by clicking on it once. Right-click on your mouse and
choose Selected Object from the menu. In the Format Data Series dialog box,
go to the axis tab. Check the "Plot Series on Secondary Axis" option. You
will now have a primary and secondary series.