Set your target temp. Then press 'set' repeatedly until 'aH' ( alarm high ) appears. Set that to the highest temp you don't want to exceed. Eg if your set temp is 20C and you don't want it to exceed 24C, set 'aH' to 24C and that's when the alarm would sound. Normally the fridge would switch on before that if your operating range is set correctly and the alarm would only go off if the fridge had packed up or you'd left the door ajar, summat like that.