OK, this may clear it up, then it may not! Taken verbatim from Embraer's ERJ-145 FCOM (instructions for manually setting bugs for approach and landing):
"For Vapp clb, set Vapp clb or Vapp, the greatest"
Allowing for Portuguese-English this is saying: IF your Vref plus additives is greater than approach climb speed, that's what you would fly on a missed approach. It doesn't seem very scientific to me, because what if you had used the maximum additive for a flap 22 landing (+20 knots) ? That is WAY above V2 flap 9 for any given weight. But that's what the man says, so I guess that's the way it's done.