No way to do this. Just put on DD turn up the DD sensitivity slider all the way up so you get promoted or demoted to Veteran + as fast as possible. Now that you're on Veteran +, go back to your sliders and put DD sensitivity all the way down to 0. Now if you're still on DD you should be stuck on Vet + at this point. For now on, whenever you bat it'll come up with your difficulty at Vet +, and it will still have your progress there. The difference is your progress will never change when you have the DD sensitivity at 0, and you'll always be on Vet +.