I have seen your posting in another thread, aren't you spreading scam here, don't you have any useful work to do despite of wasting our time, I honestly click your post since I thought it would be serious discussion, but it is not worthy one.
Why you said that he's a scammer?.
I think it should be alright if he uses an escrow service
possible. he can cancel the western union transaction right after he send the proof of payment to the escrow and escrow releases the bitcoins. there is no way escrow can confirm if the transaction is canceled or recieved by the buyer if buyer or seller isn't honest