From Xojo Documentation
| This item has been deprecated since version 2019r2 and should no longer be used.
Please use ListBox.PreventSorting as a replacement.
The user has clicked on the passed column header to sort that column or the Sort method was called. Column is zero-based.
Note that sorting is based on string comparisons. If you want to sort numbers, dates or CheckBoxes then you have to use a custom sort in the ListBox.CompareRows event.