[Al Skierkiewicz]

neutrino,
You are crossing into a dangerous area of electronics, high voltage. Without a thorough understanding of safety procedures and design requirements for electronics devices connected to the mains wiring, this should not be something you should untertake. X10 products have a variety of wireless light dimmer devices that are available for relatively little money.
I cannot stress enough, that attempting to work on mains wiring in an apartment, puts others at risk from fire and shorts.