i was thinking i could just cut the cable that produces the video signal on the gamecube and wire it to the monitor can this be done like that
In laymans terms, maybe. Depends on the "wire"...if its a SCART/RGB wire (like I said in my previous post) then yes, but with the help of an LM1881 circuit.
If you mean trying to hookup a composite signal (the yellow wire that goes to your TV), then nope. At least not without the help of some other composite->rgb converter.
Again, please read the FAQ.