CODE-SCHNIPSEL

Option Explicit
' ****************************************************************
' Autor/en und Original-Quelltext unter:
' https://www.online-vba.de/vba_abhcomboboxen.php
' Verwendung der Quelltexte auf eigene Gefahr!
' Es gelten die Nutzungsbedingungen von https://www.online-vba.de
' ****************************************************************

Const lSTARTZEILE As Long = 2

Private Sub UserForm_Initialize()
    Call FillComboBox1
End Sub

Private Sub FillComboBox1()
    Call OVBAde_FillComboBoxFromTableColumn(Tabelle1, 1, ComboBox1)
    If ComboBox1.ListCount >= 1 Then ComboBox1.ListIndex = 0
End Sub

'Ereignisroutine, wenn sich ComboBox1 verändert -> ComboBox2 und 3 neu füllen
Private Sub ComboBox1_Change()
    ComboBox3.Clear
    ComboBox2.Clear
    If ComboBox1.ListIndex = -1 Then Exit Sub
    Call OVBAde_FillComboBoxFromTableColumn(Tabelle1, 2, ComboBox2, 1, ComboBox1.Text)
    If ComboBox2.ListCount >= 1 Then ComboBox2.ListIndex = 0
End Sub

'Ereignisroutine, wenn sich ComboBox2 verändert -> ComboBox3 neu füllen
Private Sub ComboBox2_Change()
    ComboBox3.Clear
    If ComboBox2.ListIndex = -1 Then Exit Sub
    Call OVBAde_FillComboBoxFromTableColumn(Tabelle1, 3, ComboBox3, 1, ComboBox1.Text, 2, ComboBox2.Text)
    If ComboBox3.ListCount >= 1 Then ComboBox3.ListIndex = 0
End Sub

Private Sub OVBAde_FillComboBoxFromTableColumn(ByRef oSheet As Object, _
                 ByVal lColumn As Long, ByRef oComboBox As Object, _
                 Optional ByVal lColBedingung1 As Long = 0, Optional ByVal sBedingung1 As String = "", _
                 Optional ByVal lColBedingung2 As Long = 0, Optional ByVal sBedingung2 As String = "")
  Dim z As Long
  Dim zMax As Long
  Dim bFlag As Boolean
    
    oComboBox.Clear
    zMax = oSheet.UsedRange.Row + oSheet.UsedRange.Rows.Count - 1
    
    For z = lSTARTZEILE To zMax
        If Trim(CStr(oSheet.Cells(z, lColumn).Value)) <> "" Then
            bFlag = True
            
            If lColBedingung1 <> 0 Then
                If LCase(Trim(CStr(oSheet.Cells(z, lColBedingung1)))) <> LCase(Trim(sBedingung1)) Then
                    bFlag = False
                End If
            End If
            
            If lColBedingung2 <> 0 Then
                If LCase(Trim(CStr(oSheet.Cells(z, lColBedingung2)))) <> LCase(Trim(sBedingung2)) Then
                    bFlag = False
                End If
            End If
            
            If bFlag = True Then
                Call OVBAde_FillNonDuplicatesToComboBox(oComboBox, oSheet.Cells(z, lColumn).Value)
            End If
        End If
    Next z
End Sub

Private Sub OVBAde_FillNonDuplicatesToComboBox(ByRef oComboBox As Object, ByVal sAddText As String)
  Dim i As Long
  Dim bFlag As Boolean
    
    If oComboBox.ListCount = 0 Then
        oComboBox.AddItem sAddText
    Else
        bFlag = False
        
        For i = 0 To oComboBox.ListCount - 1
            If LCase(Trim(CStr(oComboBox.List(i)))) = LCase(Trim(CStr(sAddText))) Then
                bFlag = True
                Exit For
            End If
        Next i
        
        If bFlag = False Then
            oComboBox.AddItem sAddText
        End If
    End If
End Sub