用什么在GUI界面中可以输出循环中的多个数值呢？求助~（这程序不知道如何改）
namespace WindowsFibonacci数列
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        int returnValue(int num1)
        {
            int Fibonacci = 1;
            if (num1 == 1 || num1 == 2)
            {
                return 1;
            }
            else
            {
                Fibonacci = returnValue(num1 - 1) + returnValue(num1 - 2);
                return Fibonacci;
            }
        }
        private void btn_Click(object sender, EventArgs e)
        {
            int n,z,j;
            n = int.Parse(tBox.Text);
            z = 1;
            for (j = 1; j <= n; j++)
            {
                z = returnValue(j);
                MessageBox.Show(z.ToString());
            }
           
        }
    }
}