auto repeat the up/down arrow key?

Question

in firefox when im inside a input textbox and press down the up/down arrow key it doesn't autorepeat. how can i make that happen and control how many keypress it will fire up per sec?

UPDATE: i use:

$('#search_view #search').live('keydown', function(event) {
    if(event.keyCode == 40) {
       // code
    }
});

but it just execute the code one time..i would like it to repeat when holding down the down-arrow.