เรียนผู้รู้ C# ช่วยแนะนำโค้ด การกดปุ่มเดิมแต่ค่าใส่ต่าง textbox กัน

        bool focus_txtbx1, focus_txtbx2;
        private void button1_Click(object sender, EventArgs e)
        {
            if (focus_txtbx1 == true)
            {
                this.textBox1.Text = "Focus Textbox1 insert data to textbox 1";
                focus_txtbx1 = false;
            }

            if (focus_txtbx2 == true)
            {
                this.textBox2.Text = "Focus Textbox2 insert data to textbox 2";
                focus_txtbx2 = false;
            }
        }

        private void textBox2_MouseDown(object sender, MouseEventArgs e)
        {
            focus_txtbx2 = true;
        }

        private void textBox1_MouseDown(object sender, MouseEventArgs e)
        {
            focus_txtbx1 = true;
        }

int val, total;
private void button1_Click(object sender, EventArgs e)
{
this.button1.Text = "5";
val = Convert.ToInt32((this.button1.Text));
total = total + val;
this.textBox1.Text = Convert.ToString(total);
}