I have a chart that needs two sets of data to be presented relative to a
fixed Y. My 'Y' axis is 'fixed' (in this case depth) the X axis
values/series need two seperate scales (in this case 1, pressure readings and
2, an arbitrary point value.) Ideally I would like the pressure axis (1st X)
to be at the top of the chart, arbitrary point values along the bottom (2nd
X) of the chart.

The chart is a standard type - XY scatter

Thanks for any help or ideas