Elevators are made up of two doors... one for the elevator part, and one for the room transition

Room#going to - Bitflag (I used E0 and F0) - 03 00 00 00 00 0000 0000 <-- AREA TRANSITION DOOR
0000 F8 07 00 03 00 00 0004 0000 <-- ELEVATOR DOOR

AND if you want your elevator to come at a different X position, you just have to change the 5th value (its labeled X, not to hard to understand eh?) to whatever screen # you want the elevator to appear at. (ex. first screen from the left = 00, second = 01, etc.)

And make sure the elevator enemy is set up correctly to!

D73F (it's an elevator*)
[Special] = 2C00
[Speed] = 0000/0001 for down/up
[Speed 2] = Y position to make the elevator first appear when entering the room on an elevator. 0018 is a common value for elevators going down into a room. 0Z40 works quite well for elevators going up into a room, where Z is the screen just below where you emerge from.

*Do not include this in the Enemy Allowed list or it will crash your room.
**Door tiles with a RoomID of 0000 must be directly underneath the elevator, or you won't be able to stand on and use it.
***Elevators need 2 door in their path to function correctly. More information on this is included with the door editor.

That SHOULD work...