How could I send a click to the active window? Someone told me that the SendInput command did it, but I dont quite understand how it works.

[code]
Imports System.Runtime.InteropServices

Public Class Mouse

Public Declare Function SendInput Lib "user32" _
        Alias "SendInputW" (Integer nInputs, _
<MarshalAs(UnmanagedType.LPArray)>_
        INPUT pInputs(), _
        Integer cbSize)
) As Integer

End Class

<StructLayout(LayoutKind.Explicit)> _
Public Struct INPUT
  <FieldOffset(0)>_
  Public mi As MOUSEINPUT
  <FieldOffset(0)>_
  Public ki As KEYBOARDINPUT
  <FieldOffset(0)>_
  Public hi As HARDWAREINPUT
End Struct

' Since you only want the mouse input, I'm only converting that one:
<StructLayout(LayoutKind.Explicit)>_
Public Struct MOUSEINPUT
  <FieldOffset(0)>_
  Public dx As Integer
  <FieldOffset(4)>_
  Public dy As Integer
  <FieldOffset(8), MarshalAs(UnmanagedType.U4)>_
  Public mouseData As Integer
  <FieldOffset(12), MarshalAs(UnmanagedType.U4)>_
  Public dwFlags As MouseEventFlags
  <FieldOffset(16), MarshalAs(UnmanagedType.U4)>_
  Public time As Integer
  <FieldOffset(20)>_
  Public dwExtraInfo As IntPtr
End Struct

' I said there is a MouseEventFlags enumeration.  This is based on #defines in winuser.h.  It is:
<Flags()>_
Public Enum MouseEventFlags
  MOUSEEVENTF_MOVE = &H0001    ' mouse move */
  MOUSEEVENTF_LEFTDOWN = &H0002    ' left button down */
  MOUSEEVENTF_LEFTUP = &H0004      ' left button up */
  MOUSEEVENTF_RIGHTDOWN = &H0008      ' right button down */
  MOUSEEVENTF_RIGHTUP = &H0010        ' right button up */
  MOUSEEVENTF_MIDDLEDOWN = &H0020      ' middle button down */
  MOUSEEVENTF_MIDDLEUP = &H0040        ' middle button up */
  MOUSEEVENTF_XDOWN = &H0080        ' x button down */
  MOUSEEVENTF_XUP = &H0100          ' x button down */
  MOUSEEVENTF_WHEEL = &H0800          ' wheel button rolled */
  MOUSEEVENTF_VIRTUALDESK = &H4000          ' map to entire virtual desktop */
  MOUSEEVENTF_ABSOLUTE = &H8000        ' absolute move */
End Enum
[/code]

That is the declaration set for the Windows API in Visual Basic .NET.  If you have questions as to how to use it, refer to the MSDN Library.