I know Jon has already given you the steps to align two axis but a worked
out example using Centigrade and Farenheit is at

Single Chart Dual Axis
http://www.tushar-mehta.com/excel/ch...0graph%20dual%
20axis.htm

As far as the other issue goes, you can use color and text to indicate which
series goes with which chart. For example, if you have only one series on
each axis, simply color the axis and the corresponding series the same
color. If you have multiple series on each axis, add a textbox that tells
the reader which series goes on which axis.

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article ,
says...
i am trying to chart 2 different sets of data:

1. average temperature for various cities in both celsius and fahrenheit.
PROBLEM: if i have celsius on the primary x axis and the fahrenheit on a
secondary x axis it gives me 2 columns. i want one column per city which will
give me the temp in celsius on the primary x axis and the corresponding
fahrenheit temperature on secondary y axis (conversion of celsius to
fahrenheit done with formula of celsius temp*9/5+32). can this be done?

2. i am charting rainfall in 5 cities over 12 months but the data range is
very wide. one of the cities has 10x more rain than 3 of the other cities.
this makes it almost impossible to read the chart. if i plot that city on a
secondary axis, when someone else looks at my chart, how can they know what
city corresponds to primary x axis values and what corresponds to secondary x
axis values? it is very confusing.

fern