Man, 20 minutes? I'm impatient.
Assuming you remember how to use Radiant, here's a quicky:
1) make your func_mover. BE SURE it's a func_mover. Func_static's work too but they don't work correctly when moving (had lots of fun with this years ago!)
2) THE CHEATER WAY: put a target_null where you want mover to go. Put a target_null where you want the target_null to start (most likely where you create the func_mover).
3) set the settings on the func_mover for speed, time, accel, whatever. D3RAdiant has info on what each means.
4) jot down the names of the func_mover & the null's.
5) Save the map.
6) make a .script file in the same folder as the map. IE if the map is "maps/game/mover.map" put the script in "maps/game/mover.script"
7) setup your script.
I've attached an example map & script for you. I also recommend the handy dandy D3 script help file: http://www.moddb.com/members/thehappyfriar/downloads/doom-3-reference-page
Just extract the .zip to your maps folder & dmap it and it will work.