I wouldn't treat one coral. I would treat the whole tank. Here are a couple of links on how to treat with interceptor,
I suggest reading these two articles first before starting your treatment..
The test: The test thread
The cure: The Cure link
Also check out my blog. I have chronicaled my treatment (see the link at the bottom in my signature).
Finding the interceptor was the hard part. My vet dosen't carry it and I have a small dog. If you have a dog, take the article to your vet and explain what you want to do. If you don"t have a dog find a freind who does and present the information to his vet. You will need the Interceptor White. A box of six is around $50.00.
Good luck,
Dave-