You may want to check out this thread: http://www.wiichat.com/nintendo-wii-...er-things.html
I have that same monitor but I have found it very hard to get it all in progress. Not only do we need the VGA box (which you have?) but we also need the Wii composite cables (which are very hard to get your hands on atm).
I think also the Gamecube composite cables will work just fine, but don't take my word.