All you have to do is a simple trade, Gengar will evolve automatically, then you just send the Gengar back.I can't help yet but i might be able to soon. I wont need the national dex to help you, will I?
You ca't evolve Gengars.
Or am I missing something...
OK, are you available at the moment?I can help now and return it.
My fc is 4811-2796-2641
Name HIROMI