Can you re-enable areas once used?

[Nevicar]

Basically right now I have the area set to inactive. I have two sets of areas that are both right next to each (Area_4 and Area_6) other that do the same thing, close the door.

This is the best way I can sum up the way I want it to work, and the way I thought it through while attempting to code it:

1) Player enters the room, Area_4, and the door closes behind him, that function is gone and used.

2)The player then leaves the room without collecting the key which does not activate (Area_3) the other area in the room to use that when the player passes inside of it, making the door close worthless.

3) The player leaves the room and then collides with Area_7 and this area is supposed to check the player for the key and if he has it Area_6 stays inactive, but if he doesn't it becomes active.

Hope that didn't sound snobby and pretentious in the way I worded it out, I appreciate the help and know that I do need to think things through before delving into coding it all.