>>>As I move up and down the list in the combo box the selection under the cursor highlights. At the point the list item highlights I would like to run a procedure that displays the description of the item as a tool tip text.

>>This is not going to work, because InteractiveChange() fires only when you actually click on the item in dropdown portion of combobox, not when you are moving the mouse cursor over it.

Yes it will work, since the request was for an action to occur when you move up and down the list - not when the mouse cursor is moved.
How would you do that, BTW? (Not sarcastic - real question)