Private Sub Workbook_Open()
    Set dict = CreateObject("Scripting.Dictionary") '?????????
    With Sheets(1)
      last_row = .Cells(.Rows.Count, "D").End(xlUp).Row
      rng = .Range("D2:D" & last_row)
      For i = 1 To UBound(rng, 1)
        dict(rng(i, 1)) = 0
      Next i
      v = Application.Transpose(dict.keys) '???????????
    End With
    Load UserForm1
    With UserForm1
        .ComboBox1.List = v
        .Show
    End With
End Sub

With Sheets(1)
  lr = .Cells(.Rows.Count, "D").End(xlUp).Row
  ReDim arr(1 To lr, 1 To 3) <<<<<<<<<<<<<<
  i = 1
  For r = 2 To lr
    If .Cells(r, "D") = pr Then
      arr(i, 1) = Cells(r, "A")
      arr(i, 2) = Cells(r, "B")
      arr(i, 3) = Cells(r, "C")
      i = i + 1
    End If
  Next
  nmax = i - 1
End With

Private Sub UserForm_Initialize()

    Dim lng As Long
    Dim col1 As Collection
    Set col1 = New Collection
    Set sh = ThisWorkbook.Worksheets(1)
    
    With sh
        LR = .Range("A" & .Rows.Count).End(xlUp).Row
        For lng = 2 To LR
            On Error Resume Next
            col1.Add CStr(.Cells(lng, "A").Value), CStr(.Cells(lng, "A").Value)
            If Err.Number = 0 Then
                Me.ComboBox1.AddItem (.Cells(lng, "A").Value)
            End If
            Err.Number = 0
        Next
    End With
    
End Sub