Any one have experience training Blue Heelers?

Dont let him practice chasing stock.  You can use a tie out when you are actively working with the horses.  He cant get in trouble and it may help him learn self control.  You will often see stock dogs tied to fences for periods of time during training.   Every time he chases, it will take you that much longer to get him to stop the chase behavior. 
 
You can also start working him on lead doing basic obedience near the horse, initially outside the fenced areas, later in those areas.  If he comes from working stock, then shutting down his herding instinct will be quite a challenge.

I am certainly NOT letting him practice chasing stock.  The horses don't care (much) but I can't risk him getting kicked or working them up to the point where they run through a fence.
 
He was tied this AM and PM when they went in and out.  We tied him where he could see them and see us and that seemed to help.  Weirdly, when we milk the cows he is terrified of them and doesn't do anything.
 
I'm hoping to find a way to teach him HOW to work stock on command, when appropriate.  It is helpful with the bulls/cows.
 
Does your dog work stock?

If you want to learn to herd you may wish to check out the AHBA (American Herding Breeds Association) website.  Go to the judges directory link.  Check for judges in your area.  Most have phone numbers or email contacts.  These folks usually know what herding resources are available in any given area.
 
Yes I herd but more as a hobby herder than daily working stock dog.  Dess does work in moving stock, keeping them off me when feeding, holding them on the wall for trimming etc.  I am also slowly starting to compete in herding competitions.
 
You really need experienced help with herding.  Green dogs and green handlers usually end up with problems.  Depending on your area you may want to check out  Kent and Lori Herbel NE,  Cappy Pruett CO,  they do a lot of cattle dogs.  Larry Painter is also a cattle dog guy. He does lots of training camps at his place in MO

Don't be put off by the fact that your dog is scared of the stock he's supposed to be a natural at working.  Sometimes you'll get an individual that is feeling pressure from the stock so strongly that he'll need some encouragement to stay in contact.  It is impossible for anyone except an expert to tell the difference between this and a dog that is genuinely and permanently handicapped by a fear of stock or a lack of interest.

So we come back to taking your dog to see a qualified instructor.  It's best if you can find someone who either has a wide experience over many years of teaching, training, and handling dogs - or else find someone who has a lot of exerience training dogs to do what you will need specifically. 

So, for instance, I know a guy here who isn't necessarily a big trial winner and doesn't train a lot of outside dogs, but his dogs help him run a huge dairy operation.  If I wanted a dog to do dairy cow work, he'd be a good resource.  But someone who has only ever worked dog broke calves in trials, even if they train professionally, might be a less good option for me.  Even if the guy who worked his dogs on dairy cattle didn't want to do formal lessons, I'd want to cultivate a mentoring relationship with him if at all possible to trouble shoot operation-specific issues that might come up over the course of  my dog's training.

Good luck!