edit a cell in a listbox?

Can one click on a listbox cell and edit it?
Can I catch the cell clicked event and place a textfield the same width and height as the cell over top of the cell and edit it?

You can do inline editing of ListBox cells. See ListBox.EditCell and the ListBox webinar for specific examples.

Also, see Examples/Desktop/Controls/ListBoxExample included with Xojo.

If i want all cells editable must I loop through each cell and set its editable property? Can’t I use -1 for a wildcard?

You can set each column to editable. That allows you to edit every cell in that column. So you only have to loop over the columns, if you want to set every cell to editable.