Need to cancel a hooked keypress

Imports System
Imports System.Windows.Forms
Imports System.Runtime.InteropServices

Public Class Form1

    Private Const APPCOMMAND_VOLUME_MUTE As Integer = &H80000
    Private Const APPCOMMAND_VOLUME_UP As Integer = &HA0000
    Private Const APPCOMMAND_VOLUME_DOWN As Integer = &H90000
    Private Const WM_APPCOMMAND As Integer = &H319

    <DllImport("user32.dll")> Public Shared Function SendMessageW(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

    End Function

    'I'm leaving the Mute Sub in for future reference
    Private Sub Mute()
        SendMessageW(Me.Handle, WM_APPCOMMAND, Me.Handle, New IntPtr(APPCOMMAND_VOLUME_MUTE))
    End Sub

    Private Sub DecVol()
        SendMessageW(Me.Handle, WM_APPCOMMAND, Me.Handle, New IntPtr(APPCOMMAND_VOLUME_DOWN))
    End Sub

    Private Sub IncVol()
        SendMessageW(Me.Handle, WM_APPCOMMAND, Me.Handle, New IntPtr(APPCOMMAND_VOLUME_UP))
    End Sub

    Public Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Integer) As Integer
    Dim WithEvents Tmr As New Timer
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Tmr.Interval = 100
        Tmr.Start()
    End Sub
    Private Sub Tmr_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Tmr.Tick
        Tmr.Stop()
        If CBool(GetAsyncKeyState(Keys.ControlKey)) And CBool(GetAsyncKeyState(Keys.Up)) Then
            IncVol()
        ElseIf CBool(GetAsyncKeyState(Keys.ControlKey)) And CBool(GetAsyncKeyState(Keys.Down)) Then

            DecVol()
        End If
        Tmr.Start()
    End Sub

    Private Sub ShowHide() Handles Me.Shown
        Me.Hide()
    End Sub

End Class