Ah, the fresh smell of an obvious scam. 
Of course. Please say this:
"I promise I will return 1 btc for the 0.5 btc within one week."
Once done, I will send the bit coins.
I'm most certain that at least some people will not understand your message."I promise I will return 1 btc for the 0.5 btc within one week."
Once done, I will send the bit coins.