keyless entry remote question

Curious...
If you get a used car that has keyless entry and it is missing the remote
(key fob)..
You buy a replacement remote and program it...
If someone else has the original ..would it still unlock the vehicle if a
replacement has been newly programmed?

Been reading that most, if not all, remotes have to be programmed at the
same time..
So if you program a new/replacement remote...the original shouldn't work?
(unless programmed at same time)
Is this correct?

"M78Ultra" <M78Ultra.TakeThisOut@REMOVEtriad.rr.com> wrote in message
news:47116e3e$0$16456$4c368faf@roadrunner.com...
> Curious...
> If you get a used car that has keyless entry and it is missing the remote
> (key fob)..
> You buy a replacement remote and program it...
> If someone else has the original ..would it still unlock the vehicle if a
> replacement has been newly programmed?
>
> Been reading that most, if not all, remotes have to be programmed at the
> same time..
> So if you program a new/replacement remote...the original shouldn't work?
> (unless programmed at same time)
> Is this correct?
>

From http://auto.howstuffworks.com/remote-entry2.htm , the old remote should
not work with the system reprogrammed. Of course, someone will reply who
knows someone who knew someone who had a friend and it did work.

C R