I realize that I use the word «arbitrary» a lot on my blog posts, but then I think, «so what?». Anyway, this blog post is mostly a remake on another blog post, the one called «A truly dynamic tooltip«. When I wrote that blog post, I had struggled a lot to get the effect I wanted, but even though I learned a lot in the process I ended up convinced that it was better to stay out of calculation groups when building such a chart. Well, this is no more. Calculation groups, are ususal, are just fine. You just need to know how to use them.