Private Sub UserForm_Initialize()

    Dim  As Range,  As Range
    Dim ׸ As New Collection, ׸ As Variant
    
    Set  = Range("D3", Cells(Rows.Count, "D").End(xlUp))

    On Error Resume Next
    
        For Each  In 
            ׸.Add Item:=.Value, Key:=.Value
        Next

    On Error GoTo 0

    With ComboBox1
        
        For Each ׸ In ׸
            .AddItem ׸
        Next
    
        .ColumnWidths = .Width
        .ListWidth = .Width
    
    End With

End Sub