When did Batman become a Green Lantern?

Either he was loaned the ring by a Green Lantern to safeguard it or it was an Elseworlds title. And Batman is gone oblitrated by Darkseid's Omega beams (wink, wink). And neither company will do it, why kill a character than can bring b ack when sales are down and milk a few more mini series out of him. The only thing that will stop this is if we as fans refuse to buy their bull s**t!