myGB_show = function(caption, url, /* optional */ height, width, callback_fn)
{
	var options =
	{
		caption: caption,
		center_win: true,
		height: height || 200,
		width: width || 330,
		fullscreen: false,
		callback_fn: callback_fn,
		reload_on_close: false
	}
	var win = new GB_Window(options);
	return win.show(url);
}