GB_myShow = function(caption, url, /* optional */ height, width, callback_fn) {
	    var options = {
    	    caption: caption,
    	    center_win:true,
        	height: height || 300,
	        width: width || 400,
    	    fullscreen: false,
        	show_loading: false,
	        callback_fn: callback_fn
    	}
	    var win = new GB_Window(options);
    	return win.show(url);
	}