I think that some strict teachers would be UNhappy with that sentence. It sounds as if the rules are performing calculations. So it should probably be changed to something like: "When performing calculations, you / one / people should observe certain rules." ***** For example, "While walking down the street, an accident happened." Of course, the accident was not walking down the street. So we need to say: While walking down the street, I saw an accident happen right before my eyes.

It looks spot on to me Nina. No need to rehash. However your question should use the word "official" rather than "officially". For example: Does the use of the word "when" in the sentence make it sound official?

That sentence is perfect.