what to do now?

Drive a 1993 Mercedes 190e mileage is 85000...Ok experts...My Mercedes Benz Multi Rib Belt was squealing a few weeks ago. The old handy man hubby replaced it (after much cussing and complaining about not enough room to work, blah blah blah)....well the belt is back to squealing and he has tried to tighten it, and thinks its as tight as it will get. Any suggestions...aside from trading in my hubby and car?