I ran into a similar situation and this is what I did.
I set up a Scheduled Task in Windows to open a web page that I built and keep on my home computer. All that web page contains is a java redirect to my subscriptions.php.
I set the task to run every night at midnight, all I have to do is make sure my computer is on.
Here's the redirect code in case you need it:
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
redirTime = "50";
redirURL = "http://www.yoursite.com/cron/php/subscriptions.php";
function redirTimer() { self.setTimeout("self.location.href = redirURL;",redirTime); }
// End -->
</script>
</head>
<BODY onLoad="redirTimer()">
</body>
</html>