Load

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Load : Form
    {
        string textBox1_Focused, textBox2_Focused;
        public Load()
        {
            InitializeComponent();
        }

        private void Load_Load(object sender, EventArgs e)
        {

        }

        private void button_click(object sender, EventArgs e)
        {
            if (textBox1_Focused == "yes")
            {
                Button bu = (Button)sender;
                textBox1_Result.Text = textBox1_Result.Text + bu.Text;                
            }
            else if (textBox2_Focused == "yes")
            {
                Button button = (Button)sender;
                textBox2_Rult.Text = textBox2_Rult.Text + button.Text;
            }
        }
        
        private void txtAccNo_Click(object sender, EventArgs e)
        {
            textBox1_Focused = "yes";
            textBox2_Focused = "no";
        }

        private void txtAmount_Click(object sender, EventArgs e)
        {
            textBox1_Focused = "no";
            textBox2_Focused = "yes";
        }

        private void txtAmount_Click()
        {
            MessageBox.Show("");
            textBox2_Rult.Focus();
        }

        private void button12_Click(object sender, EventArgs e)
        {
            Hide();
            Form1 open = new Form1();
            open.Show();
        }

        private void button13_Click(object sender, EventArgs e)
        {

        }

    }
}