YOUR marriage might be on the rocks, but call a new RTHK radio phone-in devoted to on-air discussion of family problems and you could win a toaster. The Social Welfare Department is offering $10,000 worth of home appliances in a bid to tune life-education programmes on to a more commercial wavelength. And if the thought of people's problems being aired in return for a new rice cooker makes your hair curl, don't worry - hair dryers are on offer, too. Fourteen hour-long Harmonious Life programmes will be broadcast live from April 24, covering such diverse subjects as human relationships, sex education and home management. Their aim, say co-organisers the Family Life Education Publicity Campaign, is to help people handle problems that could undermine family relationships. But Welfare Department officials thought an incentive was needed to cook up public interest in the shows and quickly warmed to the idea of offering listeners electrical appliances. Now callers will be awarded prizes for the best positive suggestions in helping relationships work, according to Family Life Campaign chairman Miss Chung Woon-cheung. Others might even be rewarded just to cheer them up, she said. But those calling with serious problems needing more detailed counselling would always be referred to trained professionals for help. A Welfare Department spokesman said the move was a legitimate ploy in attracting listeners. ''Commercial phone-in programmes do this all the time to get people interested,'' the spokesman said. ''But the callers will have to demonstrate they have been listening to the programme to be eligible for a prize.'' Winning callers also get to go to a party to ''help them get communications going'', say organisers. But they'll be hoping the gathering doesn't resound to tales of divorcing couples battling for custody of their new toasters.