You can extend the range of your lock/unlock buttons on your key by touching the key to a bone ( ) in your body. Your bones apparently help transmit the signal.

Try pushing the metal part of the key against your skull or squeeze it firmly with your thumb while you're on the other side of the parking lot (200 - 300 yards away) and it will open. If you don't do this your range is probably about 50 yards.

I can actually open mine from the 5th floor of my office building when the car is 20 cars away in the parking lot.

Caution: If anyone sees you do this you'll look pretty stupid. However, your windows and sunroof can be opened 30 seconds earlier as you approach your car on a hot day!