Taking off and landing?

I'm trying to get my custom air transport (based off of the Goblin Zeppelin) to do these to add realism; might anyone know how I can change the unit's height in realtime, with or without triggers?

(ie go from Movement Height 270 when within [x] range of the loading units to 0, then ascending to Movement Height 270 at that same point; no probs if it can't ascend "on the fly" [if given a movement order as it takes on passengers])

There's a trigger called "Animation - Set flying height."

I haven't done any trigger for a long time, but it would look something like..

Events: A unit enters a transport.
Actions: Set flying height of (Transporting unit) to 0 at speed 2000
Wait .5 seconds
Set flying height of (Transporting unit) to (default flying height of (Triggering unit)) at speed 2000

Unfortunately, I tried it out, didn't work :( haven't changed the unit's speed from the Zeppelin's, so what exactly do I need to use where you have "speed 2000"?