Creating a rect/region by triggers

If this isnt possible by mostly simple means, please don't tell me, I don't feel like going through tons of triggers or JASS. Anyways, how do you create a rect or region by triggers? (I don't know how they are different, but which one should I use for making it so that units of type X cannot leave the region/rect I create?) I can do the making it so that the units cannot leave ( a unit leaves rect/region, blah blah blah) but I couldn't seem to find "create region/rect". Thanks in advance, I hope this all made sense.

regions are the ones with enter/leave events.

You create a region with CreateRegion and then add points or rects to it. You can even substract.

Now the can't leave thing would be hard anyways, maybe just pathing blockers?

Well the spell is like Locust Swarm, where the units only move in a certain area, but I didn't want to use Locust swarm becuase, it's not a locust swarm spell. This isn't vital to the spell, I just thought It would be easier and cooler if the beetles only moved in that area. Oh well, no big deal. Thanks anways Vex.