Secondary axis without showing data

[ChillyAnn]

I have a rainfall chart.

I want the primary vertical axis in mm and the secondary in inches.  I do not want any data to show for the secondary axis.

I'm sure this was easy in Excel 95 or some version long ago, but with Office 365 I'm failing.

Suggestions please?

[#2]

@ChillyAnn 

You do need an extra series to create a secondary axis, but it can coincide with the existing one.

See the attached demo workbook.

[#3]

Thanks Hans.

How did you make the second data not show in the chart? I did eventually find the combo chart, but the inch data sat on top of the column of mm data. The only way I could hide it, was to make it no fill, no border. Is that the only way?

[#4]

@ChillyAnn 

One series is displayed exactly on top of the other, so it completely hides the other one.

Setting one of the series to No Fill, No Line is another way of doing it.