Excel 2007.

How can i indicate on a chart which series is using which y-axis when I have
a secondary axis? For example I have several series on a line chart, some
using the primary axis and some using the secondary axis. If I use the legend
it bungs them all together with no indication which axis which line is using
- I can change their order in the legend but this doesn't really help. This
seems to be a fundemental flaw with the legend - how are you supposed to tell
what is happening on a chart when you have no idea which y-axis is used by
each line??? The only way I can see to do it is to get rid of the legend
(obviously a useful feature then!) and create my own legends out of text or
shape boxes.