The first and most important thing is DO NOT go to the puppy. It reinforces his bad behavior. If you go to him, he will think if he barks/whines, he will get attention. Can you close the door to the room? I would suggest that so he can't see what he is missing. If not, no big deal. Also, buy a Kong. Fill the Kong with some kibble, a couple treats (not to many), and then seal it with peanut butter. Freeze it overnight. He will be distracted by his new "toy". Since it is frozen, it will take a long time for him to finish it. I have two boxer puppies and the issue went away after a few days with the combination of ignoring them and giving them Kongs to distract them. The hardest time for me was when I started crating them separately. They missed their cuddle buddy : ) They did eventually get over it. They are 4.5 months now and we haven't had a problem since about 12 weeks.
Guinness- 3/12/11 Fawn Male
Bailey- 3/12/11 Flash Fawn Female