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private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            ComboBox
                cb = sender as ComboBox;
            TextBox
                tb = new TextBox();

            if (cb == comboBox1)
            {
                tb = textBox7;
            }
            if (cb == comboBox2)
            {
                tb = textBox6;
            }
            if (cb == comboBox12)
            {
                tb = textBox2;
            }
            if (cb == comboBox3)
            {
                tb = textBox8;
            }
            if (cb == comboBox4)
            {
                tb = textBox9;
            }
            if (cb == comboBox5)
            {
                tb = textBox10;
            }
            if (cb == comboBox6)
            {
                tb = textBox11;
            }
            if (cb == comboBox7)
            {
                tb = textBox12;
            }
            if (cb == comboBox8)
            {
                tb = textBox13;
            }
            if (cb == comboBox11)
            {
                tb = textBox14;
            }

            tb.Enabled = !(cb.SelectedIndex > 0);
            tb.Text = (cb.SelectedIndex > 0) ? "" : tb.Text;
        }