VBA 2 abhängige Dropdowns - Comboboxen

Private Sub ListBox1_Click()
ListBox2.Clear
For i = 2 To Sheets(1).Cells(Cells.Rows.Count, ListBox1.ListIndex + 1).End(xlUp).Row
ListBox2.AddItem Sheets(1).Cells(i, ListBox1.ListIndex + 1)
Next
End Sub

Private Sub UserForm_Initialize()
For i = 1 To Sheets(1).Cells(1, Cells.Columns.Count).End(xlToLeft).Column
ListBox1.AddItem Sheets(1).Cells(1, i)
Next
ListBox1.ListIndex = 0
End Sub