There's not a simple formula, you compare het and homo forms of every trait, you will be using multiple switches depending on that, then to do complexes you basically rewrite the calculation part to fit it. Only way I could figure it out at least.
Don't listen to them up above, there's alot more we can do with the calculators, hopefully in a few months I can put out the next step... learning new languages is driving me nuts and I lost motivation for a while, I've been slowly working on it though.