Have you thought about or tried some sort of intervention? Or do you already know this would not work? I am sure there are professional intervention people out there who could help you.
Have you ever watched the show "Intervention" on A&E TV? They actually are successful most of the time at getting their loved ones to at least go to rehab for 90 days. Sometimes they stick with it, sometimes they don't. But it usually gets the loved to sober up long enough to see what they have done to their loved ones. I think that hits home for many of them--to see how badly they hurt their family.