Corn is one of the few plants where we eat the next generation and not the current one. This means what the male parent is influences how the corn will taste.
This site
http://www.omafra.gov.on.ca/english/...cts/90-126.htm has a bunch of detail.
Basically each of the Se or SH2 corns need to be pollinated by a variety that has the same sugar gene as the mother plant and not one of the others.
Now how can we accomplish this? We can keep them separated. How far, 500+ feet is the recommended distance, or you can do it by time. I think it's around 10 days.
Let me explain this in terms of a dog. How do you keep you prized poodle Fifi from getting pregnant by Killer the neighbor hood mutt. You can keep them separated, but it only matters when she is in heat. The rest of the time they can hang out and play together an she isn't going to get pregnant. It also doesn't matter if she is already pregnant.
Now back to the corn. It doesn't come into "heat", but it does have a fertile period. A time when the pollen is ripe and the silk is ready to be pollinated. As long as the time of fertility for the Se corn and the Su(normal) corn doesn't over lap then it doesn't matter that they are close.
I also assume that if the Se corn is ready a week before the normal corn then most of it will be pollinated before the normal corn pollen ripens.