Benutzeräktivität innerhalb eines bestimmten Programmes überprüfen mit VB.Net

Public Class Form1

    Private Prozess As System.Diagnostics.Process
    Private Inaktiv, Meldung, Beenden As Integer

    <Runtime.InteropServices.StructLayout(Runtime.InteropServices.LayoutKind.Sequential)> _
    Public Structure LASTINPUTINFO
        Public cbSize As UInteger
        Public dwTime As UInteger
    End Structure

    <Runtime.InteropServices.DllImport("USER32.DLL")> _  
    Private Shared Function GetLastInputInfo(ByRef ii As LASTINPUTINFO) As Boolean
    End Function

    Public Function GetIdleTime() As Long
        Try
            Dim lastInPut As New LASTINPUTINFO()
            lastInPut.cbSize = CUInt(System.Runtime.InteropServices.Marshal.SizeOf(lastInPut))
            If GetLastInputInfo(lastInPut) Then
                Dim el As Long = lastInPut.dwTime
                Dim ui As Long = (Environment.TickCount - el)
                ' Overflow  
                If ui < 0 Then
                    ui = ui + UInteger.MaxValue + 1
                End If
                Return ui
            Else
                Throw New ApplicationException("Timespan")  
            End If
        Catch ex As Exception
            Beep()
        End Try
    End Function

    Public Function GetIdleTimeSpan() As TimeSpan
        Return New TimeSpan(GetIdleTime() * 10000)
    End Function

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        If Prozess.HasExited = False Then
            Prozess.Kill()
        End If
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Timer1.Interval = 100 'ms  
        Timer1.Enabled = True
        Prozess = System.Diagnostics.Process.Start("notepad.exe")  
    End Sub

    Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Label1.Text = Me.GetIdleTime.ToString
        Inaktiv = Int(Label1.Text)
        Meldung = 10000
        Beenden = 20000
        If Prozess.HasExited = False Then
            If Meldung - Inaktiv = 0 Then
                MsgBox("Bitte benutzen Sie '...' wieder, da sonst das Programm ohne zu speichern in 10 Sekunden geschlossen wird. Durch diesen Vorgang gehen alle nicht gespeicherten Daten verloren! Sie werden jedesmal nach 10 Sekunden inaktivität aufgefordert, wieder Eingaben zu machen!", MsgBoxStyle.Critical)  
            ElseIf Beenden - Inaktiv <= 0 Then
                Prozess.Kill()
                Close()
            End If
        Else
            Close()
        End If
    End Sub

End Class