The platform is probably just a func_door, and the button is a func_button.

Just make the platform brush, select it, press Ctrl+T and choose func_door. Set the angle to the direction you want it to move. Give it a name, too, like "bob".

Also create your func_button out of a brush the same way. Set the target to "bob".

No. Why?

If the platform moves around more than you're leading me to believe, it may need to be a func_train.

This should explain it:

http://collective.valve-erc.com/index.php?ent=func_train

In my experience, though, func_trains misbehave in CS. You might want to try a func_tracktrain instead, I'm not really sure.

It's what makes the sun shine!