GB_myShow = function(caption, url, height, width, callback_fn) {
    var options = {
        caption: caption,
	height: height,
	width: width,
	center_win: true, 
        fullscreen: false,
        show_loading: true,
        callback_fn: callback_fn
    }
    var win = new GB_Window(options);
    return win.show(url);
}