Type POINTAPI
X As Long
Y As Long
End Type

Type MSLLHOOKSTRUCT
pt As POINTAPI
mouseData As Long
flags As Long
time As Long
dwExtraInfo As Long
End Type

#If VBA7 Then
#If Win64 Then
Declare PtrSafe Function WindowFromPoint Lib "user32" (ByVal Point As LongLong) As LongPtr
#Else
Declare PtrSafe Function WindowFromPoint Lib "user32" (ByVal xPoint As Long, ByVal yPoint As Long) As LongPtr
#End If
Declare PtrSafe Function GetClassName Lib "user32" Alias "GetClassNameA" (ByVal hwnd As LongPtr, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long
Declare PtrSafe Function GetParent Lib "user32" (ByVal hwnd As LongPtr) As LongPtr
Declare PtrSafe Function GetActiveWindow Lib "user32" () As LongPtr
Declare PtrSafe Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As LongPtr)
Declare PtrSafe Function GetCursorPos Lib "user32" (ByRef lpPoint As POINTAPI) As LongPtr
Declare PtrSafe Function SetFocus Lib "user32" (ByVal hwnd As LongPtr) As LongPtr
Declare PtrSafe Function IsWindow Lib "user32" (ByVal hwnd As LongPtr) As Long
Declare PtrSafe Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" (ByVal idHook As Long, ByVal lpfn As LongPtr, ByVal hmod As LongPtr, ByVal dwThreadId As Long) As LongPtr
Declare PtrSafe Function CallNextHookEx Lib "user32" (ByVal hHook As LongPtr, ByVal nCode As Long, ByVal wParam As LongPtr, lParam As Any) As LongPtr
Declare PtrSafe Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As LongPtr) As LongPtr
Dim hwnd As LongPtr, lMouseHook As LongPtr
#Else
Declare Function WindowFromPoint Lib "user32" (ByVal xPoint As Long, ByVal yPoint As Long) As Long
Declare Function GetClassName Lib "user32" Alias "GetClassNameA" (ByVal hwnd As Long, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long
Declare Function GetParent Lib "user32" (ByVal hwnd As Long) As Long
Declare Function GetActiveWindow Lib "user32" () As Long
Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Declare Function GetCursorPos Lib "user32" (ByRef lpPoint As POINTAPI) As Long
Declare Function SetFocus Lib "user32" (ByVal hwnd As Long) As Long
Declare Function IsWindow Lib "user32" (ByVal hwnd As Long) As Long
Declare Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" (ByVal idHook As Long, ByVal lpfn As Long, ByVal hmod As Long, ByVal dwThreadId As Long) As Long
Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Long, ByVal nCode As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Long) As Long
Dim hwnd As Long, lMouseHook As Long
#End If

Const WH_MOUSE_LL = 14
Const WM_MOUSEWHEEL = &H20A
Const HC_ACTION = 0

Dim oComboBox As Object

Sub SetComboBoxHook(ByVal Control As Object)
Dim tPt As POINTAPI
Dim sBuffer As String
Dim lRet As Long

Set oComboBox = Control
RemoveComboBoxHook
GetCursorPos tPt
#If Win64 Then
Dim lPt As LongPtr
CopyMemory lPt, tPt, LenB(tPt)
hwnd = WindowFromPoint(lPt)
#Else
hwnd = WindowFromPoint(tPt.X, tPt.Y)
#End If
sBuffer = Space(256)
lRet = GetClassName(GetParent(hwnd), sBuffer, 256)
If InStr(Left(sBuffer, lRet), "MdcPopup") Then
SetFocus hwnd
#If Win64 Then
lMouseHook = SetWindowsHookEx(WH_MOUSE_LL, AddressOf MouseProc, Application.HinstancePtr, 0)
#Else
lMouseHook = SetWindowsHookEx(WH_MOUSE_LL, AddressOf MouseProc, Application.Hinstance, 0)
#End If
End If
End Sub

Sub RemoveComboBoxHook()
UnhookWindowsHookEx lMouseHook
End Sub

#If VBA7 Then
Function MouseProc(ByVal nCode As Long, ByVal wParam As LongPtr, lParam As MSLLHOOKSTRUCT) As LongPtr
#Else
Function MouseProc(ByVal nCode As Long, ByVal wParam As Long, lParam As MSLLHOOKSTRUCT) As Long
#End If

Dim sBuffer As String
Dim lRet As Long

sBuffer = Space(256)
lRet = GetClassName(GetActiveWindow, sBuffer, 256)
If Left(sBuffer, lRet) = "wndclass_desked_gsk" Then Call RemoveComboBoxHook
If IsWindow(hwnd) = 0 Then Call RemoveComboBoxHook

If (nCode = HC_ACTION) Then
If wParam = WM_MOUSEWHEEL Then
#If Win64 Then
Dim lPt As LongPtr
CopyMemory lPt, lParam.pt, LenB(lParam.pt)
If WindowFromPoint(lPt) = hwnd Then
#Else
If WindowFromPoint(lParam.pt.X, lParam.pt.Y) = hwnd Then
#End If
On Error Resume Next
If lParam.mouseData > 0 Then
oComboBox.TopIndex = oComboBox.TopIndex - 1 '<---u can change this to change the scrolling speed upwards
'u can change "TopIndex" to "listIndex" if you want to change the value instead of hovering it, do not use the dynamic listFillrange if u do!
Else
oComboBox.TopIndex = oComboBox.TopIndex + 2 '<---u can change this to change the scrolling speed downwards
'u can change "TopIndex" to "listIndex" if you want to change the value instead of hovering it, do not use the dynamic listFillrange if u do!
End If
On Error GoTo 0
End If
End If

MouseProc = CallNextHookEx(lMouseHook, nCode, wParam, ByVal lParam)
End Function

he combobox code (view code to the combobox):
Option Explicit

'optional
Dim ComboBoxRange As Range
Dim myRange As Range
Dim NumRows
'optional
Private Sub ComboBox1_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
Call SetComboBoxHook(ComboBox1)
End Sub

Private Sub ComboBox1_LostFocus()
Call RemoveComboBoxHook
End Sub

'optional, this code is for a dynamic list, do not use if u changed TopIndex to ListIndex!
'importent note...u need a dynamic list to begin with if u want to use it!
Private Sub ComboBox1_Change()
Set myRange = Range("Q:Q") 'the range of data
NumRows = Application.WorksheetFunction.Count(myRange)
'////////////////////////////////////////////////////////////////
Set ComboBoxRange = Range(Cells(4, 17), Cells(3 + NumRows, 17))
'my data starts at range Q4, Q = 17, A=1, change this according to the range you want to change
'////////////////////////////////////////////////////////////////
ComboBox1.ListFillRange = ComboBoxRange.Cells.Address
ComboBox1.DropDown
End Sub
'optional

Option Explicit
Private Sub ComboBox1_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(ComboBox1) = True
End Sub
Private Sub ComboBox1_LostFocus()
    EnableMouseScroll(ComboBox1) = False
End Sub
Private Sub ComboBox2_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(ComboBox2) = True
End Sub
Private Sub ComboBox2_LostFocus()
    EnableMouseScroll(ComboBox2) = False
End Sub
Private Sub ComboBox3_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(ComboBox3) = True
End Sub
Private Sub ComboBox3_LostFocus()
    EnableMouseScroll(ComboBox3) = False
End Sub

Option Explicit
Private Sub ComboBox1_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(ComboBox1) = True
End Sub
Private Sub ComboBox1_LostFocus()
    EnableMouseScroll(ComboBox1) = False
End Sub

Option Explicit
Private Sub Workbook_Open()
    Sheet1.InitComboEvents
End Sub

Option Explicit
Public WithEvents cBox As MSForms.ComboBox

Private Sub cBox_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(cBox) = True
End Sub

Private Sub cBox_LostFocus()
    EnableMouseScroll(cBox) = False
End Sub

Option Explicit

Private Sub Workbook_Open()
    Sheet1.InitComboEvents
End Sub

Option Explicit
Dim ComboColl       As Collection

Public Sub InitComboEvents()
    Dim c           As clsComboEvents
    Dim ctrl        As OLEObject

    Set ComboColl = New Collection

    For Each ctrl In Me.OLEObjects

        If TypeOf ctrl.Object Is MSForms.ComboBox Then
            Set c = New clsComboEvents
            Set c.cBox = ctrl.Object
            ComboColl.Add c
        End If

    Next ctrl

End Sub

Option Explicit
Private Sub Workbook_Open()
    Sheet1.InitComboEvents
End Sub

Private Sub cBox_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
    EnableMouseScroll(cBox) = True
End Sub