There's really no one exercise that will help you with panic attacks. It differs from people to people. As a matter of fact, exercise isn’t the only thing to help you relax. Doing relaxing things can really do wonders and it can be as simple as reading a book to more demanding tasks such as hiking to even breaking things or squeezing a tennis ball and even going to sleep or taking a nap.
For example, driving can be a source of relaxation to some, but to others it can be a source of a panic attack. Also, walking can help people relax, but to some it's a source of the panic attack. It really depends on where you live, what you're doing, and most importantly why you're having the panic attacks in the first place. If you are having panic attacks due to stress of time, then putting in a schedule for dance can further complicates thing due to the limited time.
I would look into the source of the panic attack, rather than trying to find ways to suppress it. If you are really stressed, and you feel dancing will help, then do it and see if it can help you. I, however, doubt that it will benefit you in the way you wish. I doubt it mainly because I feel most people live in a very stressed environment when they're in school or making life changes. I would wait until the source of the panic attack is found, and then if you wish to continue your dancing as a means to relax, then do it.