(function($){
    $.fn.set_ds = function(options) {
		var defaults = {
			step : 100,
			num : 2
		};
		var options = $.extend(defaults, options);
		var $ds = $("#" + $(this).attr("id"));
		var side_num = $ds.find("td.ds_side").length;
		var current = 0;
		var $arr = $ds.find("a.arr");
		var $base = $ds.find("div.b_head");
		var $bck = $ds.find("a.bck");
		var $fwd = $ds.find("a.fwd");
		var $scr = $ds.find("div.ds_scroll");
		
		$bck.click(function(e) {
			e.preventDefault();
			ds_go(-1);
		});
		
		$fwd.click(function(e) {
			e.preventDefault();
			ds_go(1);
		});
		
		$base.bind("mousedown", function() {
			return false;
		});
		
		function ds_go(to) {
			current = current + to;
			if(current < 0) {current = 0};
			if(current > side_num - options.num) {current = side_num - options.num};
			$scr.animate({left:options.step * -current},200,set_arrs);
		}
		
		function set_arrs() {
			if(current == 0) {
				$bck.hide();
				$fwd.show();
			} else if(current == side_num - options.num) {
				$bck.show();
				$fwd.hide();
			} else {
				$bck.show();
				$fwd.show();
			}
		}
		set_arrs();
	}
})(jQuery);