C#

groupBox1.Controls.Add(this.CheckedListBoxE);
groupBox1.Controls.Add(this.CheckedListBoxD);
...

const UInt32 SW_HIDE = 0 ;
const UInt32 SW_SHOWNORMAL = 1 ;
const UInt32 SW_NORMAL = 1 ;
const UInt32 SW_SHOWMINIMIZED = 2 ;
const UInt32 SW_SHOWMAXIMIZED = 3 ;
const UInt32 SW_MAXIMIZE = 3 ;
const UInt32 SW_SHOWNOACTIVATE = 4 ;
const UInt32 SW_SHOW = 5 ;
const UInt32 SW_MINIMIZE = 6 ;
const UInt32 SW_SHOWMINNOACTIVE = 7 ;
const UInt32 SW_SHOWNA = 8 ;
const UInt32 SW_RESTORE = 9 ;
const UInt32 SW_SHOWDEFAULT = 10 ;
const UInt32 SW_FORCEMINIMIZE = 11 ;
const UInt32 SW_MAX = 11 ;

[DllImport("user32.dll")]
static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

using System;
using System.Timers;
using System.Drawing;
using System.Windows.Forms;

public class test : System.Windows.Forms.Form
{
	Button b;
	System.Timers.Timer t;

	public test()
	{
		InitializeComponents();		
	}
	
	public void InitializeComponents()
	{
		b = new Button();
		b.Text = "Hide Me";
		b.Click += new EventHandler(bClick);
		
		t = new System.Timers.Timer();
		t.Elapsed += new ElapsedEventHandler(elapsed);
		t.Interval = 3000;
		t.Enabled = true;
		
		this.Controls.AddRange(new Control[] {b});
	}	

	private void bClick(object sender, EventArgs e)
	{
		this.WindowState = FormWindowState.Minimized;
		this.Visible = false;
		this.ShowInTaskbar = false;
	}

	private void elapsed(object source, ElapsedEventArgs e)
	{
		MessageBox.Show(this.Handle.ToString());
	}
	
	[STAThread]
	public static void Main()
	{
		Application.Run(new test());
	}
}