Third Axis in Excel Chart

Short-short version
Challenge:
Creating a chart with three Y axes

Disclaimer:
Best practice dictates to keep each chart in a single set of units and scale, to avoid confusion.

Having said that.... I'll move on

I created a second chart as an additional layer on top of the first one with the additional data.

Difficulties:
Avoiding the numbers of the Y axes of different layers from writing on each other


Solution:

1. Set the font of the Y axis of chart #1 to be superscript (offset = +50%) and of chart #2 as subscript (offset=-50%)
2. Set the lines, X axis and chart boarders of chart #2 to transparent
3. Set the range of all three Y axes to fit the same number of tick marks - this will keep a single set of horizontal lines 
4. To make it clear (or clearer) to viewers what scale goes with what series - set the colors of the series to match the colors of the numbers of the Y axes
5. Place chart #2 carefully on top of chart #1

Enjoy!

(I'll add pictures soon to make this clear)

---

---

Long version follows...

Building a third Y axis in Excel can be done using some tricks.
This one uses adding an additional chart as a second layer chart on top of the existing chart.
With some manipulation and using transparent lines and fills, this can be done.

Let's say we are creating a chart for a driver, and we have the cost, distance, and average speed of a series of trips that we would like to show (against recommended practices) on a single chart.

1. We'll create one chart with all three parameters set against the date, as an XY chart, setting the cost and distance on the primary axis, and the speed on the secondary (don't worry, we'll move the distance in a couple of steps), giving us something like this:
   
    
2. Copy the chart, and paste it on the spreadsheet below the first one. We'll call this chart #2
3. Remove the Distance series from chart #1 (click on a data point or the line of this series, and press <Del>)
4. Remove the Cost and Speed series from chart #2.
   now comes the fun part
5. Change the scale of the Y axis of chart#2 to fit the same number of tick marks as the Y axis of chart #1. I assume here that you have already done this for the primary and secondary axes (pronounced ax-sees?).
6. Make sure the scale of the X axis remains the same in both charts through this manipulation. what we have to do is:
1. Make the lines, background and X axis of chart #2 transparent
2. Move the Y axis values of chart #2 and the primary Y axis of chart #1 so they don't write over each other. 

Disclaimer:
Best practice dictates to keep each chart in a single set of units and scale, to avoid confusion.

Having said that....
Real world tends to dictate otherwise

Problem:
Displaying data on vastly different scales makes it hard to see the data and notice the trend that the chart is trying to show.

Alternate solutions:
1) Display the data on a series of charts, each with a single Y scale and  units, and paste them on top of each other using the same X scale (Remove the X scale from all but the lowest chart).