It's quite simple, it doesn't require a modchip but you have to be quite fast:
You should now be able to play it.
Insert a random European GameCube game in the Wii Choose the Disc channel in the Wii menu Point at the "Start" button While you're pressing the start button, eject the disc out of your Wii Push the A-button. Take out the European GameCube disc and insert a NTSC game.
Here's a YouTube video showing how it's done: