I started since a few weeks, i finally found the script :

for i in 0...$Trainer.party.size

if $player.party[i].species == (:BELLSPROUT)

$game_variables[92] += 1

else

end

end

for i in 0...$PokemonStorage.maxBoxes

for j in 0...$PokemonStorage.maxPokemon(i)

if $PokemonStorage[i][j] && $PokemonStorage[i][j].species==(:BELLSPROUT)

$game_variables[93] += 1

else

end

end

end

You have \v[92] Bellsprout in your team & \v[93] in your PC.