This I did by using the method in this link.
http://www.mmowned.com/forums/wow-ex...se-banker.html
If you follow that method you can only do it once.
But I have found a way to do it as many times as you like! Simply have your Haunted Memento guy out and make sure you can see him. Then bring out any non-combat pet. Then deposit the Haunted Memento into the bank. As soon as its deposited the banker despawns. Go to the next banker, take it out, rinse and repeat.
I was doing this as soon as the banker would repawn again. Alot of people got mad. Id suggest trying to make not too obvious.