Hi ,
You don't need a helper cell ; what you need is a separate helper worksheet , where all the calculations can be done using helper cells / columns. Without this , deriving all of what you want is probably work for a paid professional.
The reason you have given is not good enough ; every good dashboard is done with the help of helper cells / columns / worksheet ; an interactive dashboard which had thousands of rows of data to deal with , and complicated array formulae to do all the complex calculations in single cells would no longer be interactive ; changing one input data cell would take 10 minutes for the dashboard to update itself.
You need to change your expectations.
The alternative is VBA , but even with VBA , developing all the 20 measures that you want displayed would take a fair amount of code.
Narayan