Perhaps you could spray/dab/touch a dog repellant/pepper/mustard paste/soap... something YUK (harmless)on the knobs AND make sure he's got lots of his own play things to keep him occupied...he could miss you when you're out and go looking for a distraction to help him with his lonliness ...give him an old teddybear too...one of those white soft bears from Opp shops/Salvation Army shops etc...just a few dollars. All the best.MaryP