My Friend is addicted to World of Warcraft What do I Do?

Hi, my 14 year old friend has recently taken up playing WoW (World of Warcraft) an online role playing game. I know about this game as i have had bad personal experiences with it before. I lost my old best friend to this game and I have seen it split apart families. I accepted the fact that he played it but made him swear on his life that he would not get addicted. Well today i asked him if he would like to hang out after school and guess what he said? "Nah" so i asked Aww why not? Presuming that he had work and he said "umm i wanna play WoW." This shattered me. Again this god damn game is ruining my social life and i need any advice I can get. No stupid answers like get new friends please because i'm not like that and we are both a part of a group that i am not leaving as i have other good friends in it. Any suggestions will be appreciated, thanks.