Script? I'd rather not. We aren't very good at scripting, at least not me.
Well, it's your decision, obviously.
- You can leave the space black and don't warn players about it, which will cause frustration as can be seen by Nicholiathan's post further above.
- You can forego the idea of pitch black spaces altogether, as hinted by dingosky in his reply.
- You can leave a light at the entrance area, so that people won't have difficulties finding the way back.
- You can script the entrance as described above, which wouldn't be very hard to do, even if you never used scripts before, since both "scripted door" and "obtaining a decision from the player" are things that have been done many times, so there should be lots of examples.
Like Socucius Ergalla said: "There are a few ways we can do this and the choice is yours."