private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
if (dataGridView1.CurrentCell.ColumnIndex.Equals(3) && e.RowIndex != -1){
if (dataGridView1.CurrentCell != null && dataGridView1.CurrentCell.Value != null)
MessageBox.Show(dataGridView1.CurrentCell.Value.ToString());
}