[plt-scheme] Frame in MrEd around widgets

Hi all,

I've done this once but I just can't remember which class to
use. How can I make a frame like the ones in Preferences,
browser tab with a label like "HTTP Proxy"?

Cheers,
-- 
Paulo Jorge Matos - pocm at sat inesc-id pt
Engº de Informática e Computadores
INESC-ID - Grupo SAT - MathSAT