Selected Answer
Generally speaking - and that is all I can do since you don't provide a reference ("this week" doesn't help because the tutorials aren't dated) - a helper column should be designed to be hidden, meaning it should contain a formula that requires no maintenance. It can be hidden in many ways including placing it on a dedicated sheet which itself is hidden although that makes the task of not requiring maintenance more difficult. The gist of my advice is to think about ways to live with the hidden column rather than how to avoid it.
Which isn't to say that I would accept a hidden column. I never have and I guess I never shall. However, simply put, since VLOOKUP - despite its need for a helper column - provides the easiest solution to the problem, all others require more effort. Depending upon the detail of your circumstances, it might be possible to create a formula, albeit one much more complicated than VLOOKUP, but my weapon of choice would be VBA, perhaps a UDF (User Defined Function).