Turning Off Auto-Select In Combo Boxes

Is there a way to force a combo box that automatically selects an option when 
you arrow through it not to do this? I know how to do it in multi-select lists 
and such, but not so much in combo boxes. The shift plus down arrow doesn't 
seem to work here. Is there any other way? It's tedious having to wait for a 
page to load each time when I'm going through a combo box of 349 items.

Thanks so much.

Samara

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