Реализация на C#

hwnd h = FindWindow(nil,'Безымянный - Блокнот');

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        string nametable = "";
        public Form2()
        {
            InitializeComponent();
        }
 
        private void Form2_Shown(object sender, EventArgs e)
        {
            Form3 nameget = new Form3();
            nameget.Show();
            this.Enabled = false;
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    public partial class Form3 : Form
    {
        public Form3()
        {
            InitializeComponent();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
             //Здесь нужно изменить значение переменной nametable в Form2  
        }
    }
}

Form2.Visible = false;

this.Visible = false;

// For Windows Mobile, replace user32.dll with coredll.dll
 [DllImport("user32.dll", SetLastError = true)]
 static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
 
 // Find window by Caption only. Note you must pass IntPtr.Zero as the first parameter.
 
 [DllImport("user32.dll", EntryPoint="FindWindow", SetLastError = true)]
 static extern IntPtr FindWindowByCaption(IntPtr ZeroOnly, string lpWindowName);

using System.Runtime.InteropServices;

Form3 form3;
form3.Visible = false;