#3 Getting number of the selected element in ComboBox

[Simon Bachmann]

It would be useful to have the possibility to get the
index of the selected element on a ComboBox.
It's possible to get tis index with
`.combox subwidget listbox index anchor' (.combox is a
ComboBox, of course...(-; )
but this works only if the element was selected
directly by the user. Changing the value of the
ComboBox from "inside"with the `pick' command, the
listbox selection is not changed, and thus getting the
index this way may give an erroneous value.