如何改变stm32L0的RTC的wakeup time？

STM32L0的RTC的wakeup time在RTC初始化为固定值，有时希望这个wakeup time可以改变，请教大家如何才能成功改变？

初始化代码如下，没有问题

static void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */
  /** Initialize RTC Only
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  if (HAL_RTC_Init( hrtc) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enable the WakeUp
  */
  if (HAL_RTCEx_SetWakeUpTimer_IT( hrtc, 59, RTC_WAKEUPCLOCK_CK_SPRE_16BITS) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

改变的代码如下，不成功

HAL_RTCEx_DeactivateWakeUpTimer( hrtc);

__HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);

HAL_RTCEx_SetWakeUpTimer_IT( hrtc, g_UT_SleepTime, RTC_WAKEUPCLOCK_CK_SPRE_16BITS);