unclicking elevator buttons

i've always thought that being able to un-click an elevator button would be very cool (if any of you are like me and are prone to hitting the wrong floor, or maybe, even the alarm bell a few times). so of course, when i saw someone at work correct his mistake by pressing 3 elevator buttons at the same time, to nicely erase his 'wrong' floor, i thought (and exclaimed) - WOW!

so at night i got to my hotel and happily decided to try it out. started off at L, and my room's on 34. just for kicks, to see if it'll erase my choice, i hit 3, 6, and 33 at the same time.

hmm. 34 was still lit. (moved from 3 to 6).

decided to try again, but geez, i guess i should have tried floors higher than 34 just in case i was wrong. so i hit 39, 41 and 44. didn't work. tried again. 42, 43, 46.

darnit. now a ton of buttons are lit. for one person in the elevator.

i guess it doesn't work with ALL elevators. i felt sorry for the dude who got in at 34 and was going up.