How do I Program the Key for a Mercedes E320?

1. Place your new key into the ignition of your Mercedes E320.
2. Hold down the 'Lock' button on the key fob.
3. Remove the key from the ignition while maintaining your hold on the 'Lock' button.
4. Push the 'Unlock' button on the key fob five times, consecutively. Do not release your hold on the 'Lock' button while pushing the 'Unlock' button.
5. Release your hold on the 'Lock' button to complete the programming process.