Have you tried Rescue Remedy? Visa is an extremely high drive dog (being a Belgian), and I could rarely take her anywhere without her being a freak. She is not the least bit dog aggressive, but when a high drive Belgian sees another dog running offleash, it's general instinct is to want to kill it or just have a complete panic attack. It was never an issue of calming her -- she didn't need to be calm -- she just needed to stop her behaviour. The Rescue Remedy did just that. Now I can take her to agility and have her be completely focused on me and the task we are doing. She is no longer looking elsewhere and screaming and biting my hands and clothes and completely freaking out (not an anxiety thing, just a Belgian thing. God forbid another dog have fun in the presence of an onleash Belgian). I had tried everything before that. Tons of exercise, herbal sedatives, everything. All it did was make her tired and therefire even worse. The Rescue Remedy doesn't do that --- She's completely herself without the freakiness. I love it, I recommend trying it for all behaviour problems. My friend had a cat that would bite (not out of meanness, it would make little "love bites"), and when she started giving him rescue remedy, the behaviour stopped.

You can buy it at natural health food stores. I bought mine at Nature's Fare for $15 and it's lasting me forever.

Good luck!