Is spook proofing possible?

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From: Nina Vasiliev 
Email: rmack@inreach.com

Hi there,

I'm the one who fell off during a So, I'm out for the rest of the year at least.  

I'm looking for ground exercises to keep my horseand me from going crazy. 
A friend suggested to teach Ramere to spook in place rather than jumping to the side. 
(Too good to be true?)
Now Ramere is usually great.  
No reaction to flapping tarps, trucks (and I mean TRUCKS) flying by, 
or dogs barking while charging us.
Nope, he  spooks at ...rocks?...logs?  
We were walking a flat walk, nothing to get excited about.  
The horse in front of us was calm. 
We had trotted for about 3 miles prior so he wasn't "hot to go."  
The trail was flat and boring.  He jumped to the side without a warning.  
Then he was fine.  His spooks are always over quickly. 
He will even spook while we're going at speed.  
Then as suddenly, he'll continue to trot along.  

My friend said I should teach him to spook in place but I'm not sure how, or if that's possible.

Any thoughts, suggestions?

Nina Vasiliev