<script>

var active_page_id = 4;

function getPosition(id)
{
	switch(id)
	{
	case 1:
	  return position = "321px";
	  break;
	case 2:
	  return position = "407px";
	  break;
	case 3:
	  return position = "496px";
	  break;
    case 4:
	  return position = "556px";
	  break;
	case 5:
	  return position = "619px";
	  break;
	default:
	  //
	}
}

function slideOver(id)
{
    $("#top_menu_arrow").stop().animate({
            left: getPosition(id)
        }, 700);
}

function slideBack()
{
   $("#top_menu_arrow").stop().animate({
            left: getPosition(active_page_id)
        }, 700);
}

$(document).ready(function() {
  // initiate active section in menu
  slideOver(active_page_id);
});

</script>

usage:
<a href="#" onMouseOver="slideOver(5)" onMouseOut="slideBack()" />