Optimisation hint:
If you run a query to fill the list box, then fill it with the other data you want to display on the form, but in hidden columns (column widths of 0).
Then as the user selects the item from the dropdown, you use after update or click events to take the hidden columns data of the selected item and put it into the text box fields on the form. Makes it look faster on seleccting, but a little slower (negligable) on filling the dropdown.