From Xojo Documentation
The Change event is called when the row selection is changed by the user or by code.
The Change event handler is called when the row selection changes, not when cell contents change.
The Change event handler is called in response to the following user actions:
- When the Listbox is clicked to give it the focus
- When an empty row in the ListBox is clicked
- When a cell is clicked even if it already is selected and the column is not editable
- When a row is clicked to change the selection
If a column is editable, clicking in a cell calls the Change event but a second click to get an insertion point does not. Clicking on a header or a checkbox does not call the Change event.
Also, a programmatic change to ListBox.ListIndex also triggers the Change event.