$().ready( function() {
    $("#driver_select").mouseup(function() {
        showDrivers();    
    });
});

function showDrivers() {
    var count = $('#driver_select').val();
    if (count == 5) {
       for (i = 1; i <= 4; i++) {
           $('div.driver_'+i).slideUp();
		   $('div.driver_'+i+' input.sex').removeClass('required');
        }
    }
    else {
        if ($('div.all_drivers').is(':hidden')) {
            $('div.all_drivers').slideDown();
        }
        for (i = 1; i <= 4; i++) {
            if (i > count) {
                $('div.driver_'+i).slideUp();
				$('div.driver_'+i+' input.sex').removeClass('required');
			}
            else {
                $('div.driver_'+i).slideDown();
				$('div.driver_'+i+' input.sex').addClass('required');
			}
        }
    }
}