using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public int a, b, c;

        public Form1()
        {
            InitializeComponent();
        }

        private void JHandler(CheckBox checkBox, ref int value, TextBox textBox)
        {
            if (checkBox.Checked) {
                value += Convert.ToInt32(checkBox.Tag);
            } else {
                value -= Convert.ToInt32(checkBox.Tag);
            } textBox.Text = Convert.ToString(value);
        }

        private void CheckBox_A_Click(object sender, EventArgs e)
        {
            JHandler((sender as CheckBox), ref a, textBox1);
        }

        private void CheckBox_B_Click(object sender, EventArgs e)
        {
            JHandler((sender as CheckBox), ref b, textBox2);
        }

        private void CheckBox_C_Click(object sender, EventArgs e)
        {
            JHandler((sender as CheckBox), ref c, textBox3);
        }
    }
}