Public Class Form1
 
    Public Structure Point
        Public X As Integer
        Public Y As Integer
    End Structure
 
    Public Structure Msllhookstruct
        Public Location As Point
        Public MouseData As Integer
        Public Flags As Integer
        Public Time As Integer
        Public ExtraInfo As Integer
    End Structure
 
    Private Delegate Function HookProc(nCode As Integer, wParam As Integer, ByRef lParam As Msllhookstruct) As Integer
 
 
    <System.Runtime.InteropServices.DllImport("user32.dll", SetLastError:=True)> _
    Private Shared Function SetWindowsHookEx(ByVal hookType As Integer, ByVal lpfn As HookProc, ByVal hMod As IntPtr, ByVal dwThreadId As UInteger) As IntPtr
    End Function
 
    <System.Runtime.InteropServices.DllImport("user32.dll", SetLastError:=True)> _
    Private Shared Function CallNextHookEx(ByVal hhk As IntPtr, ByVal nCode As Integer, ByVal wParam As IntPtr, ByRef lParam As Msllhookstruct) As IntPtr
    End Function
 
    Public Hook As IntPtr
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Hook = SetWindowsHookEx(14, AddressOf Proc, Process.GetCurrentProcess().MainModule.BaseAddress.ToInt32(), 0)
    End Sub
 
    Private Function Proc(nCode As Integer, wParam As Integer, ByRef lParam As Msllhookstruct) As IntPtr
        If wParam = 522 Then
            Dim Delta = CShort(lParam.MouseData >> 16)
 
            If Delta > 0 Then
                ' Up
                MsgBox("Up")
            ElseIf Delta < 0 Then
                ' Down
                MsgBox("Down")
            End If
        End If
 
        Return CallNextHookEx(Hook, nCode, wParam, lParam)
    End Function
 
End Class