This one goes out to all the people who have been asked to change the way a SharePoint site looks. Management wants to know how long it will take, and you can whip that out by tomorrow, right? If you don't have time to prepare a treatise on what's involved, or if you just want to lend some extra weight to your case by quoting a blogger who was an MVP for seven years, then dive right in; this post is for you.
Yes, you can do this with an Event Receiver. You might be able to do it with a VS workflow, or possibly one of those fancy third-party tools... maybe not. But if you're a SharePoint admin with nothing but SharePoint Designer and you need to determine if a field changed, here's how.