Raising or lowering a bridge.

Is there a way to raise or lower a doodad in game? The only trigger which I could find is the advanced one in WEU, which is "create destructible at X height*, but then I would need a trigger to delete the old doodad, and my catwalk would appear to teleport up and down. A gradual slowly lowering effect would be the best. Preferably so units could remain on it while it lowers.

Here is a picture which will hopefully help with my problem
http://img176.imageshack.us/img176/3813/catwalkbk2.jpg

*my actual catwalk is made of a different doodad and does not look that bad*

Bridges are raised and lowered in game by killing and resurrecting them, I believe. Elevators, however, can be moved around up and down, so try the elevator triggers.

Creating and destroying a doodad every tick is not good optimization.
I suggest you add an animation to your bridge in which it slowly moves down or up. Another thing you can do is construct a bridge with the elevetor doodads and use their animations.