Manipulate DateTimeFormField while clikcing on radio button

Question

I've to change DateTimeFormField date according ti given condition into radio button. For example, if I select Yes, I've to set DateTimeFormField value as DateTime.now(). For N/A DateTimeFormField will be empty. I'm using setState in Yes, N/A for changing the value. The value is changing but not showing into DateTimeFormField. I mean it's not refreshing. How can I refresh the DateTimeFormField value according to Yes, N/A selection?

DateTimeFormField(
  dateFormat: DateFormat('yyyy-MM-dd'),
  mode: DateTimeFieldPickerMode.date,
  initialValue: DateTime.parse(list[index].end!),
  decoration: InputDecoration(
    isDense: true,
    contentPadding: EdgeInsets.symmetric(horizontal: 10.w, vertical: 10.h),
    hintStyle: TextStyle(color: Colors.black45),
    errorStyle: TextStyle(color: Colors.redAccent),
    border: OutlineInputBorder(),
    suffixIcon: Icon(Icons.event_note),
  ),
  onDateSelected: (DateTime value) {
    list[index].end= value.toString();
  },
)

Radio<String>(
value: list[index].yes!,
groupValue: "Y",
onChanged: (value) {
  setState(() {
    list[index].naFlag = "N";
    list[index].yes = "Y";
    list[index].yes = "Y";

    if(list[index].start== null) {
      list[index].start= DateTime.now().toString();
    }
    if(list[index].end== null) {
      list[index].end= DateTime.now().toString();
    }
  });
  list[index].yes = "Y";
  list[index].naFlag = "N";
},
activeColor: Colors.blue,
)