Shoutbox

Sure, have your script use the Microsoft.XMLHTTP activex object to connect to the internet and download a page or file that contains update information (an XML file works nicely, but other things will work too).

Here's an example of downloading a web page with XMLHTTP:
http://shoutbox.menthix.net/showthread.php?tid=56...d=617138#pid617138

You can also look at the source of any existing script that checks updates