Opening cages?

Hi!
I've got an idea for my map, but dont't know how to realize it:
At the beginning there is a cage containing some demons. When the player reaches a certain point in the map, the cage shall open, so that the demons can leave the cage.

Does anybody know if this is possible? The problem is, that it doesn't work with a lowering floor or a door, because you can't put the gate-textures as upper or lower textures...

Any idea?

Thanks,

Marky

Oh.... now I found the solution... hehe...

Thank you.