Formatting the y-axis of a chart

Ah, the light just went on.

See attached for the method mentioned by Andy applied to your chart

A dummy series with X values of the lowest value on the X axis, combined with Y values of even distribution. The data markers sit on the Y axis. Use the XY Chart Labeler tool http://www.appspro.com/Utilities/ChartLabeler.htm for easy creation of labels for the data points to the left of the markers, then remove the axis labels.

I've left the data markers for the dummy series visible, but you can set them to no markers to hide them.

Just make sure that your primary and secondary Y axes have the same Min and Max settings.