How do you stop your dog from licking

My greyhound began licking his foot a couple years ago. It started getting very raw, so we would tell him to stop. After a while, he just couldn’t stop. We then started to get concerned. We tried wrapping his foot and sour apple spray, but it didn’t stop him. He would gladly lick the spray, and chew right through the bandage. Finally, we figured out how to cover it with a sock that he couldn’t get through right away. We wrapped the bottom half of the sock in duct tape. It usually took a few days for him to work through that. We thought we found the answer.
Well, it did usually take him a long time get through it, but sometimes he would manage to pull it off. The elastikon tape that we put on would not be tight enough. We had to be careful not to put it on too tight of course. As soon as he got it off, or worked through it, he would lick his foot and ruin three days of healing in a few minutes.
After about a year of this fight, we finally decide to mention it to our veterinarian. He suggested continuing with the plan and see what happens. There was no change after a couple more months. It just seemed like it would not even start healing.
We took him back to the vet and got some antibiotics and a recommendation to soak his foot twice a day in a betadine solution. We decided to try using an e-collar. We were afraid to use that before. We keep that on most of the time so his foot can stay dry.
We have had tremendous improvement in two weeks. His foot looks great, he doesn’t seem to have the same interest in licking it anymore, and we aren’t going through socks so fast.

Update 06/05/09
He has really shown some real progress. You can hardly tell which foot has the problem. When we take the e-collar off, he ignores the foot. After a while, I guess he remembers that he is obsessive about licking it. Then we have to stop him and put the collar back on. I imagine we will be going through this routine for at least another month to ensure that his issue is over. I don’t want to go through it all again.