Vertical navigation with Garmin GPSMap 496

Has anyone here figured out how to do vertical navigation with the
Garmin GPSMap 496? (Or 495, or 395?) It sounds like a really handy
feature but I can't get it to work except in the simplest manner where
it is less useful.

Vertical navigation would be most useful around a class bravo
airspace, for example taking the VFR corridor through New York City,
where you have to do a series of step-downs in stages down to 1100
feet, the corridor, then a series of step-ups to climb back out the
other side. But I can't seem to set up my points to work with VNAV.

You can set up a series of waypoints from the MAP page by moving the
"rocker" key (up, down, left, right, arrows) in "pointer mode" to
point where you want to set a waypoint, then click-and-release the
(Enter) button, and it creates a waypoint. This can create a full
user-defined waypoint (auto-numbered 001 002 003...) which includes an
altititude field where you can set how high above the waypoint you
want to pass. But if you happen to click on a named geographical
feature on the map, (e.g. "I-95") then it will NOT create a full user-
defined waypoint there, but instead, it will just use the geographical
feature as the waypoint, but VNAV will not work with that waypoint
because it does NOT have an altitude field that you can set. And if
you happen to position the cursor on the boundary of an airspace
(which is exactly where you need your waypoints) then when you hit
(enter) it will identify the airspace for you instead of making a
waypoint! So I can't set up a chain of waypoints with a guarantee that
they will all be full user-defined waypoints.

I found a way to make all my waypoints user-defined ones. With the
aircraft sitting at the airport at its last known position (I do this
on the ground in simulator mode) I first go to the "Points" menu
Waypoint" (enter)) and fill in the fields, but before I hit [OK], I
first go to ["Show Map"], and there's my new waypoint (say "001")
located at the current location of the aircraft, I click on that "001"
and I see the word "MOVE" appear under it, then I click on the
location I want my waypoint and it moves the waypoint to that
location. I have set up a chain of waypoints in this manner that step
down and back up again in altitude. But I cannot seem to select the
first, or second, or third in the chain and do VNAV to them, it only
wants to do VNAV to the last point in the chain.

In other words, it seems like the system is designed only to be used
for your final airport destination, and I can get that to work OK,
although that is not very useful because you are almost always going
to level out in the traffic pattern and do the last descent visually,
where your VNAV would not be very useful.

Anyone else?

slehar