Hide button in a combobox dropdown

[Andrew]

When the user clicks my combobox I want to display the list but not
the button that appears to the right of the combo. This seems to be
what is implied by "fmShowDropButtonWhenNever" but infact the button
appears when the control gets focus (which I would have thought was
the purpose of "fmShowDropButtonWhenFocus").

My combo has the following properties:

Style = fmStyleDropDownList
ShowDropButtonWhen = fmShowDropButtonWhenNever

Is there another setting somewhere that I have to alter to get this to
work as expected?

Thanks a lot,
Andrew