Combo Box List

Private Sub UserForm_Initialize()
    Dim Sh As Worksheet
    Dim Rng As Range
    Dim Cell As Range
    Dim Coll As New Collection
    Dim Item As Variant
    Dim i As Long
    Dim j As Long
    Dim Temp As Variant
    Set Sh = Worksheets("Sheet1")
    Set Rng = Sh.Range("A1:A" & Sh.Range("A" & Sh.Rows.Count).End(xlUp).Row)
    ComboBox1.Clear
    On Error Resume Next
    For Each Cell In Rng
        Coll.Add Cell.Value, CStr(Cell.Value)
    Next Cell
    On Error GoTo 0
    For Each Item In Coll
        ComboBox1.AddItem Item
    Next Item
    With ComboBox1
        For i = 0 To .ListCount - 1
            For j = i + 1 To .ListCount - 1
                If .List(i) > .List(j) Then
                    Temp = .List(j)
                    .List(j) = .List(i)
                    .List(i) = Temp
                End If
            Next j
        Next i
    End With
End Sub

Private Sub UserForm_Initialize()
Dim dic As Object, e
Set dic = CreateObject("Scripting.Dictionary")
dic.CompareMode = vbTExtCompare
With Sheets("Sheet1") '<- change to suite
    With .Range("a1",.Range("a" & Rows.Count).End(xlUp))
        .Sort .Range("a1"), xlAscending
        a = .Value
    End With
End With
For Each e In a
    If Not IsEmpty(e) And Not dic.exists(e) Then dic.add e, Nothing
Next
Me.CD.List = dic.keys
Set dic = Nothing : Erase a
End Sub