[DllImport("kernel32.dll",SetLastError=true)]
static extern uint GetTickCount();
[DllImport("user32.dll",SetLastError=true)]
static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);
[StructLayout( LayoutKind.Sequential )]
struct LASTINPUTINFO
{
    public static readonly int SizeOf = Marshal.SizeOf(typeof(LASTINPUTINFO));
    [MarshalAs(UnmanagedType.U4)]
    public int cbSize;    
    [MarshalAs(UnmanagedType.U4)]
    public uint dwTime;
}
public static bool IsInputIdle(int idleTimeoutSecond)
{
  LASTINPUTINFO LInInfo;
  LInInfo.cbSize = LASTINPUTINFO.SizeOf();
  if (GetLastInputInfo(ref LInInfo) != 0)
  {
    return (GetTickCount() - LInInfo.dwTime) > idleTimeoutSecond;
  }
  else
    return false;
}

<DllImport("kernel32.dll", SetLastError := True)> _
Shared Function GetTickCount() As UInteger
End Function

<DllImport("user32.dll", SetLastError := True)> _
Shared Function GetLastInputInfo(ByRef plii As LASTINPUTINFO) As Boolean
End Function

<StructLayout(LayoutKind.Sequential)> _
Structure LASTINPUTINFO
  Public Shared ReadOnly SizeOf As Integer = Marshal.SizeOf(GetType(LASTINPUTINFO))
  <MarshalAs(UnmanagedType.U4)> _
  Public cbSize As Integer
  <MarshalAs(UnmanagedType.U4)> _
  Public dwTime As UInteger
End Structure

Public Shared Function IsInputIdle(ByVal idleTimeoutSecond As Integer) As Boolean
  Dim LInInfo As LASTINPUTINFO
  LInInfo.cbSize = LASTINPUTINFO.SizeOf()
  If GetLastInputInfo(LInInfo) <> 0 Then
    Return (GetTickCount() - LInInfo.dwTime) > idleTimeoutSecond
  Else
    Return False
  End If
End Function

function IsInputIdle(const idleTimeoutSecond: Cardinal): Boolean;
var
  LInInfo: TLastInputInfo;
begin
  LInInfo.cbSize := SizeOf(TLastInputInfo);
  if GetLastInputInfo(LInInfo)  then
    Result := (GetTickCount - LInInfo.dwTime) > idleTimeoutSecond
  else
    Result := False;
end;

Private Type LASTINPUTINFO
  cbSize As Long
  dwTime As Long
End Type
Private Declare Function GetTickCount Lib "kernel32" () As Long
Private Declare Function GetLastInputInfo Lib "user32" (plii As LASTINPUTINFO) As Long
Public Function IsInputIdle(ByVal idleTimeoutSecond As Long) As Boolean
  Dim LInInfo As LASTINPUTINFO
  LInInfo.cbSize = Len(LInInfo)
  If Not GetLastInputInfo(LInInfo) = 0 Then
    IsInputIdle = ((GetTickCount() - LInInfo.dwTime) > idleTimeoutSecond)
  Else
    IsInputIdle = False
  End If
End Function