关于Timer控件解决方法

关于Timer控件
最近在学着做图片播放的练习。
请问10张图片循环播放该怎么实现，
用了Timer控件但是每次放完10张就结束了，
有办法循环吗？

private void button5_Click(object sender, EventArgs e)     //开始播放按钮

        {

            if (Pflag)

            {

                if (txtTime.Text != "") 

                {

                    if (cbbShowType.SelectedIndex == 1)          //dropdownlist选项一：原图显示

                    {

                        timer1.Interval = int.Parse(txtTime.Text.Trim());

                        timer1.Start();                          //开始计时播放（默认速度为1000毫秒）          

                        button5.Enabled = false;

                    }

                    else

                    {

                        Form2 frm2 = new Form2();                //跳转到from2进行图片播放

                        frm2.fsi = al;

                        frm2.picPath = txtPicPath.Text.Trim();

                        frm2.mytimer = int.Parse(txtTime.Text.Trim());

                        frm2.ShowDialog();  

                    }

                }

            }

        }


        private void timer1_Tick(object sender, EventArgs e)            //计时工具

        {

            if (MM < listBox1.Items.Count)                              //如果原先保存的listbox的数值小于listbox的集合数量

            {

                if (txtPicPath.Text.Trim().Length == 3)                 

                {

                    pictureBox1.Image = Image.FromFile(txtPicPath.Text.Trim() + listBox1.Items[MM].ToString());

                    listBox1.SetSelected(MM, true);

                }

                else

                {

                    pictureBox1.Image = Image.FromFile(txtPicPath.Text.Trim() + "\\" + listBox1.Items[MM].ToString());

                    listBox1.SetSelected(MM, true);

                }

            }

            MM++;                                                     //MM数值递增