C#

// This method will convert a column number to the excel letter.
// 1 = A, 2 = B, 3 = C, ..., 27 = AA
public string ConvertExcelIndexToLetter( int column ) {
			
    System.Text.StringBuilder value = new System.Text.StringBuilder();
    const int BASE_VALUE = 26;
    int modularBase;

    while ( column != 0 ) {
    
        if( column == ( ( column / BASE_VALUE ) * BASE_VALUE ) ) {

 	    modularBase = column - ( ( column / BASE_VALUE ) - 1 ) * BASE_VALUE;
	    column = ( column / BASE_VALUE ) - 1;
	}
	else {

	    modularBase =  column - ( ( column / BASE_VALUE ) ) * BASE_VALUE;
	    column = ( column / BASE_VALUE );

	}

	value.Append( ((char)( modularBase + 64 )).ToString() );

    }
			
    return value.ToString();

}

// always remember to clean up COM objects with the Marshal class.
// I have had problems with Excel 2000 & XP not closing.  Make sure
// you call the ReleaseComObject for every COM object.
private void NAR(object o){
    try {

	System.Runtime.InteropServices.Marshal.ReleaseComObject(o);

    }
    catch{ }
    finally{
        
        if (o != null ) o = null;

    }
}

<br />
  bool IsConnecting;<br />
<br />
  [DllImport("wininet.dll", SetLastError=true)]<br />
  private static extern bool InternetGetConnectedState(ref UInt32 Flags, <br />
    UInt32 Reserved);<br />
<br />
  private void buttonStartMonitor_Click(object sender, System.EventArgs e)<br />
  {<br />
    UInt32 Flags = new UInt32();<br />
    IsConnecting = InternetGetConnectedState(ref Flags,0);<br />
    timer1.Interval = 100;<br />
    timer1.Start();<br />
  }<br />
<br />
  private void timer1_Tick(object sender, System.EventArgs e)<br />
  {<br />
    UInt32 Flags = new UInt32();<br />
    if(IsConnecting != InternetGetConnectedState(ref Flags,0))<br />
    {<br />
      IsConnecting = InternetGetConnectedState(ref Flags,0);<br />
      //Perform your process here<br />
    }<br />
  }<br />