I understand your anguish about stopping the diet Cokes... I have been addicted to Pepsi, Coke, and Dr. Pepper for 24 years. Until the week before my lap band surgery, I honestly drank 6-12 cans a day. The very last thing I had before starting my pre-op liquid diet was drink a 24 oz Pepsi. Much to my surprise, I haven't had one since, over a month and half later! Seriously, I didn't drink anything but soda, and now I'm "over it".
I never wanted to stop drinking soda because I LIKED it, but I have to say - my mindset is so much better now. I'm more able to concentrate at work, I sleep better... I'm having a lot of sucess with the band, but the icing on the cake is that I have broken a very unhealthy habit that I really didn't want to give up. I knew I had to stay away from the stuff before surgery, and after that week, I didn't crave it anymore. Now I know I can be a success!
Good luck to you! It seems like a little step, but it will enpower you to know you broke the addiction!