Difference between listbox and combo box
LISTBOX CONTROL displays a list of items from which the user can select
one or more. If the number of items exceeds the number that can be
displayed, a scroll bar is automatically added to the ListBox control.
A COMBOX CONTROL combines the features of a text box and a list box.
This control allows the user to select an item either by typing text
into the combo box, or by selecting it from the list.
DIFF::Generally, a combo box is appropriate when there is a list of suggested choices, and a list box is appropriate when you want to limit input to what is on the list. A combo box contains an edit field, so choices not on the list can be typed in this field.