well, i'm not really an expert at all, but the other day a friend of mine came round with his dog, we left him (the dog, not the friend.. ) in another room for a while, and then tried to open the door to see how they'd react... the dog seemed quite playful, didn't want to harm her at all, but she started hissing and scratched him on the face on the first possible occasion but my friend was just visiting, so maybe we did it too quickly/wrong. I know that there's a spray that makes cat calmer, that might help.. I'm sure that other people in the forum will be more helpful than I am!
Good luck and let us know how it goes (if you do it)!