sounds pretty simple:
I have a checkout form with the user providing his (billing) address.
Then by clicking a checkbox, additional fields should open for providing a shipping address.
I don't want to have both fieldsets open right from the start but the second toggling when required, since i think it's an easier checkout process asking the user something like "ship to an other address" than showing a bunch of possibly unnecessary fields.

Long story short, since i have not really a clue of JS, JQuery etc. is there a (more or less) 'ready-to-go' script i could use?
I do it in PHP right now but think it might be (again) more userfriendly not to go serverside right away.