Need to update formula to a third value

annaxi 

I'll offer a general principle in response to your question. That general principle--and you're experiencing the "Why?" behind it--is to avoid "hard-coding" variables in your formulas. 

What to do instead? One alternative--often suitable--is to use lookup tables, which you are already doing in some way, evident since you are using VLOOKUP. That makes me think that maybe a multiple dimensional table or a method to choose different tables, might work for you.

I'm attaching an example where I did this latter--to allow for different tables to be used within a single formula (to calculate the US income tax) changing the underlying table based on filing status. It's not directly applicable, but perhaps the principle in the design is.