public partial class Form2 : Form 
{ 
private System.Timers.Timer timer = new System.Timers.Timer(); 

public Form2() 
{ 
    InitializeComponent(); 
    InitStatus(); 
    timer.Interval = 4000; 
    timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed); 
    timer.Enabled = true; 
} 

void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e) 
{ 
    IntPtr hDlog = FindWindow(null, "Show"); 
    if (IntPtr.Zero != hDlog) 
    {  
 IntPtr result; 
 EndDialog(hDlog, out result); 
    } 
} 

private void InitStatus() 
{ 
    this.panel1.Controls.Clear(); 

    Form1 from1 = new Form1(); 
    from1.TopLevel = false; 
    from1.FormBorderStyle = FormBorderStyle.None; 

    this.panel1.Controls.Add(from1); 
    from1.Show(); 
} 
[DllImport("user32.dll",SetLastError=true)] 
public static extern IntPtr FindWindow(string lpClassName, string caption);

<span style="white-space:pre">  <span style="font-family: monospace; white-space: pre; background-color: rgb(240, 240, 240); ">[DllImport("user32.dll",SetLastError=true)]</span><br style="font-family: monospace; white-space: pre; background-color: rgb(240, 240, 240); "><span style="font-family: monospace; white-space: pre; background-color: rgb(240, 240, 240); ">        public static extern int PostMessage(IntPtr hWnd, int message, IntPtr wParam, IntPtr lParam);</span> 
</span> 
 
 
        [DllImport("user32.dll",SetLastError=true)] 
        public static extern bool EndDialog(IntPtr hDlg, out IntPtr nResult); 
 
        private void button1_Click(object sender, EventArgs e) 
        { 
            MessageBox.Show("corning", "Show"); 
        } 
    }