Normally you should have just one?? Why would you ever have JUST one is my question! Normally they are used to give people choices between things that are attached toa record identifier, and since people don't remember ID numbers but remember names/descriptions/etc.. you use a two column list box (at least) with one column being the identifier and the other being the name/description/etc..
As for the question. You can't click on the built in columns of the listbox, but you can make textboxes on top of the listbox. Format them so they look like labels and when people click on them you can associate an event to reorder the items in the listbox. You can also add ControlTips like "Click here to sort by X" so users can see they can change the sort order.
HTH Joe Miller
joe.miller@flotech.net