Excel User Form... Filter Combo box based on other

Private Sub ComboBox1_Change()
Dim I As Long
Dim ws As Worksheet

    Set ws = Worksheets("ComboInfo")
    ComboBox2.Clear
    For I = 1 To ws.Cells(65536, 1).End(xlUp).Row
        If ws.Cells(I, 1) = ComboBox1.Value Then
            ComboBox2.AddItem ws.Cells(I, 2)
        End If
    Next I
End Sub
Private Sub ComboBox2_Change()
Dim I As Long
Dim ws As Worksheet

    Set ws = Worksheets("ComboInfo")
    ComboBox3.Clear
    For I = 1 To ws.Cells(65536, 1).End(xlUp).Row
        If ws.Cells(I, 2) = ComboBox2.Value Then
            ComboBox3.AddItem ws.Cells(I, 3)
        End If
    Next I
End Sub

Private Sub ComboBox3_Change()
Dim I As Long
Dim ws As Worksheet

    Set ws = Worksheets("ComboInfo")
    ComboBox4.Clear
    For I = 1 To ws.Cells(65536, 1).End(xlUp).Row
        If ws.Cells(I, 3) = ComboBox3.Value Then
            ComboBox4.AddItem ws.Cells(I, 4)
        End If
    Next I
End Sub

'Erik Van Geit
'050618

'cascading comboboxes :-)
'sources in corresponding columns
  'box1 = column1 ...
'several comboboxes (see N)
  'to expand:
    'add combobox on userform
    'Const N = number of boxes
    'add Private Sub ComboBox ..N.. _Change()
Option Explicit

Const N = 4
Public flag As Boolean

Private Sub ComboBox1_Change()
If flag = True Then Exit Sub
update_comboboxes (1)
'general syntax
'update_comboboxes (Application.WorksheetFunction.Substitute(ActiveControl.Name,ComboBox,))
End Sub
Private Sub ComboBox2_Change()
If flag = True Then Exit Sub
update_comboboxes (2)
End Sub
Private Sub ComboBox3_Change()
If flag = True Then Exit Sub
update_comboboxes (3)
End Sub

Sub update_comboboxes(nr As Integer)
Dim I As Long
Dim ws As Worksheet
Dim FilterRng As Range
Dim UniqueRng As Range
Dim cell As Range

Set ws = Worksheets("ComboInfo")

flag = True
    For I = nr + 1 To N
    Controls("ComboBox" & I).Clear
    Next I
ws.Cells.AutoFilter
Set UniqueRng = ws.Range(ws.Cells(2, N + nr + 2), ws.Cells(65536, N + nr + 2).End(xlUp))

  For I = 1 To nr
  ws.Columns(1).Resize(Rows.Count, N).AutoFilter Field:=I, Criteria1:=Controls("ComboBox" & I).Value
  Next I

Set FilterRng = ws.Range(ws.Cells(2, nr + 1), ws.Cells(65536, nr + 1).End(xlUp)).SpecialCells(xlCellTypeVisible)

    For Each cell In UniqueRng
        If Not FilterRng.Find(cell) Is Nothing Then
        I = I + 1
        Controls("ComboBox" & nr + 1).AddItem cell
        End If
    Next cell
flag = False

If Controls("ComboBox" & nr + 1).ListCount = 1 Then
Controls("ComboBox" & nr + 1) = Controls("ComboBox" & nr + 1).List(0)
End If
End Sub

Private Sub userform_initialize()
Dim I As Integer
Dim LR As Long
Dim ws As Worksheet

Set ws = Worksheets("ComboInfo")

ws.Columns(N + 1).Resize(Rows.Count, N).ClearContents

For I = 1 To N
LR = ws.Cells(65536, I).End(xlUp).Row
ws.Range(ws.Cells(1, I), ws.Cells(LR, I)).AdvancedFilter Action:=xlFilterCopy, CopyToRange:=ws.Cells(1, N + I + 1), Unique:=True
Next I

LR = ws.Cells(65536, N + 2).End(xlUp).Row
Controls("ComboBox1").RowSource = ws.Name & "!" & Range(ws.Cells(2, N + 2), ws.Cells(LR, N + 2)).Address(0, 0)
    
End Sub

Private Sub Worksheet_Activate()
UserForm1.Show
End Sub

Private Sub CommandButton1_Click()
Dim ws As Worksheet
Worksheets("ComboInfo").Activate
UserForm1.Hide
Range("A1").Select
End Sub

Worksheets("ComboInfo").AutoFilterMode = False

Private r As Range, dic As Object

Private Sub userform_initialize()
Dim x
Set dic = CreateObject("Scripting.Dictionary")
With Sheets("ComboInfo")
    For Each r In .Range("a2", .Range("a65536").End(xlUp))
        If Not IsEmpty(r) And Not dic.exists(r.Value) Then
            dic.Add r.Value, Nothing
        End If
    Next
End With
x = dic.keys
Me.ComboBox1.List = x
End Sub

Private Sub ComboBox1_Change()
Me.ComboBox2.Clear: Me.ComboBox2.Clear
Set dic = CreateObject("Scripting.dictionary")
    With Sheets("ComboInfo")
        For Each r In .Range("a2", .Range("a65536").End(xlUp))
            If r = Me.ComboBox1.Value Then
                If Not dic.exists(r.Offset(, 1).Value) Then
                    Me.ComboBox2.AddItem r.Offset(, 1)
                    dic.Add r.Offset(, 1).Value, Nothing
                End If
            End If
        Next
    End With
    With Me.ComboBox2
        If .ListCount = 1 Then .ListIndex = 0
    End With
End Sub

Private Sub ComboBox2_Change()
Dim x
Me.ComboBox3.Clear
With Sheets("ComboInfo")
    For Each r In .Range("a2", .Range("a65536").End(xlUp))
        If r = Me.ComboBox1.Value And r.Offset(, 1) = Me.ComboBox2.Value Then
            x = r.Offset(, 2) & Chr(32) & r.Offset(, 3)
                Me.ComboBox3.AddItem x
        End If
    Next
End With
With Me.ComboBox3
    If .ListCount = 1 Then .ListIndex = 0
End With
End Sub