onkey event and on change with dropdown menu

i have a dropdown menu that submits a form object when the onchange event is triggered. however, i noticed that the onchange event is only triggered when users use the mouse to change the selection.

my question is what javascript on-<blank> event should i use if users, use the tab key and the arrowkeys to select an option in the dropdown menu?

for example, the dropdown menu contains a list of countries and instead of using the mouse to select a country, i use the up and down arrowkeys. how do i catch that event? onchange doesn't seem to catch it.

Probably the best way is do double the onchange event with a normal submit button. Thus, those who might have used the arrows (or those which might have javascript disabled) could submit as well