Change the location of an arrow by pressing ENTER key

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C#

I am working on a C# project and I want to change the location of an arrow by pressing ENTER key with different size of iteration for different comboBox selections. Actually it works but the problem is that I can not refresh the Form before changing comboBox Selection. I want to see iteration step by step but it moves if I change the comboBox selection. Here is the code:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {


            if (comboBox1.SelectedIndex == 0)
            {

                this.BackColor = Color.Black;
                label1.ForeColor = Color.Silver;
                label1.Text = "Environment is Space";
                pictureBox2.Image = list.Images[4];
                t = 100; // iteration amount

            }

            else if (comboBox1.SelectedIndex == 1)
            {
                this.BackColor = Color.PaleTurquoise;
                label1.Text = "Environment is Water";
                pictureBox2.Image = list.Images[3];
                t = 50; // iteration amount

            }

            else if (comboBox1.SelectedIndex == 2)
            {
                this.BackColor = Color.DarkGoldenrod;
                label1.ForeColor = Color.Firebrick;
                label1.Text = "Environment is Honey";
                pictureBox2.Image = list.Images[2];
                t = 20; // iteration amount
            }

        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {

            // Drawing arrow
            Pen pen = new Pen(Color.FromArgb(255, 0, 0, 255), 8);
            pen.StartCap = LineCap.ArrowAnchor;
            pen.EndCap = LineCap.RoundAnchor;
            e.Graphics.DrawLine(pen, x+50, 200, x, 200);

        }

        private void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
            // pressed Enter => change x
            if (e.KeyChar == (char)Keys.Return)
            {
                e.Handled = true;
                if (x < y)
                {
                    x += t;

                }
            }
        }

To be more clear:
I want like: Click-> Enter + Move-> Arrow + Click->Enter + Move -> Arrow
Now it works like: Click-> Enter + Change-> comboBox + Move->Arrow

Thanks a lot!