Way to stop the Avada Kedavra curse?

[keith.fraser at st-annes.ox.ac.uk]

No: HPFGUIDX 22543

I was thinking about Harry Potter and Dungeons & Dragons today :ducks 
flying fruit and shouts of "Geek!": and I had an idea. In D&D one way 
to stop a hostile spell is to cast the same spell back as a 
counterspell. Mightn't it be possible to hold back the Killing Curse 
by casting one of your own so that they cancelled each other out.

Just a thought.

Keith