Add onMouseOver to menu item?

I am trying to get links in my nav menu to make an image (which is outside of the nav) swap to a different image. So…

1. Is it possible to add an onMouseOver javascript event to each menu item?

2. Is there a better way to do this? I’d like to be able to detect the menu item with javascript and tell it to swap a specific image onMouseOver. This way I wouldn’t need to add the onMouseOver attribute to the menu item.