Treats. Entice your pup up & down...in & out with a favorite treat. When he obeys, praise & reward. Boxers are very smart and long on memory. He must have had a bad experience with the up & down thing along with the stairs. Your Boxer needs to be trained to walk with you by using a specially leash made just for this purpose. You can get one at most Pet Supply stores. Spend as much time as you can with your Boxer. You won't believe how fast and how much of a love affair will develop.