We've spent a lot of time implementing this ourselves for a data table containing lab analysis values. It's a big requirement from our customers. You can imagine it's pretty important to be able to match rows and columns (sample types and dates) correctly when you're looking at these values.
The planning meeting about this was pretty funny.
Boss: "So, we'll just make the headers fixed, should be easy, right?"
Developer: "Heh-heh... Yeah, we could probably get that working decently in just a couple of weeks. We'll have to test it in all the browsers, of course, and do performance tests with big data sets. It's possible that we might not be able to get it to work well enough on all platforms, so we should have a backup plan."
Boss: "Sigh. This would be so much easier in Visual Basic..."