I got this from somebody last year on TSR I think, but people keep asking for it so I thought it would be helpful to post it!
Basically you just put ur unit marks in and it tells you what AS grade and A2 grade you are on, and how many you need to get each A2 grade, really useful and usually reassuring as people realise they aren't under as much pressure as they thought they were.
It wouldn't let me upload the new Excel format, but I've got the old one on there, and that will work on anyone's computer with Micrsoft Office, any version, and if you want to save space just resave it as the new version and it's about half as much file space.