private void IncreaseValue(TextBox t)
        {
            int Value = int.Parse(t.Text);
            Value++;
            t.Text = Value.ToString();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            IncreaseValue(textBox1);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            IncreaseValue(textBox2);
        }

        private void button3_Click(object sender, EventArgs e)
        {
            IncreaseValue(textBox3);
        }