假设输入框ID是：ID_NUMBER1，ID_NUMBER2,ID_NUMBER3。

获取数据的方式是：

int number1,number2,number3;
number1 = GetDlgItemInt(ID_NUMBER1);
number2 = GetDlgItemInt(ID_NUMBER2);

number3 = number1 + number2;
SetDlgItemInt(ID_NUMBER3,number3);

将数据3设置在输入框三中。