If possible, and he does do it again, try to get it on video so you can show the vet. I doubt you could get to the vet while he's still doing it. This is what I did with my dog and the vet was very glad I had the video.
Luckily, my dog was having petit-mal seizures, so no medicine was necessary. And now since we got our second dog (in November of 2008) she has not had an episode at all.
The vet would want to know how often it is happening. Since Zoee's were not frequent (only about 2 or 3 a year) or very severe we did not have to medicate. Had they become more often or worse, then phenobarbital may have been prescribed.
I hope your pup (my mom had a min pin for 17 1/2 years) is only have petit-mal's and will not need medicine.