Perhaps someone else has a better solution than I. The only thing I can think of is a little tricky. The VGA output on your laptop is just that, an output. In order to input a video signal onto your laptop, you need some kind of TV tuner, like this:
http://www.newegg.com/Product/Product.aspx...N82E16815260023
Now, if there's a TV tuner out there that has a composite (Red, White, Yellow) input, great, but I don't know of any.
So, you have the TV Tuner, with the coaxial input for you to plug your cable into. Only you're trying to hook up your Wii, which has the afore mentioned composite cables. So, we need to get something that will convert your composite cables to a coaxial cable. Enter the RF Modulator:
http://www.amazon.com/Philips-PH61159-RF-M...r/dp/B0001GGXQI
You hook up your Wii to the RF Modulator, you hook the RF Modulator up to the TV Tuner that is plugged into the USB port on your laptop, and you're set.
Now, some things to consider on all of this:
-This does take a little technical knowledge on your part, as you will need to install the software that came with your TV Tuner card. Using the RF Modulator should be fairly straightforward.
-If you do get all of this hooked up, I have a feeling that the picture you see on your laptop might be delayed slightly, as it has to go through the RF Modulator, through the Tuner card, and processed by your laptop. I honestly can't say how much of a delay we're talking here, but if you're playing video games, it could be enough to be distracting. I just don't know.
Sorry I don't have a simpler solution, but I believe that's the route you would have to take to get it all set up.