Private Sub UserForm_Initialize()

'Заполнить уникальными значениями ComboBox1 из столбца "B"
    Arr = Range(Cells(5, 2), Cells(Rows.Count, "B").End(xlUp)).Value
    With CreateObject("Scripting.Dictionary")
        For i = LBound(Arr) To UBound(Arr)
            .Item(Arr(i, 1)) = 1
        Next
        Me.ComboBox1.List = SortArray(.Keys)
    End With

    'Заполнить уникальными значениями ComboBox2 из столбца "C"
    Arr = Range(Cells(5, 3), Cells(Rows.Count, "C").End(xlUp)).Value
    With CreateObject("Scripting.Dictionary")
        For i = LBound(Arr) To UBound(Arr)
            .Item(Arr(i, 1)) = 1
        Next
        Me.ComboBox2.List = SortArray(.Keys)
    End With

End Sub

'Процедура для сортировки массива методом пузырька
Function SortArray(ByRef a As Variant)
    Dim i As Long, j As Long
    Dim t As Variant

    'standard bubble sort loops
    For i = LBound(a) To UBound(a) - 1
        For j = i + 1 To UBound(a)
            If a(i) > a(j) Then    'change to < for descending order
                t = a(i)
                a(i) = a(j)
                a(j) = t
            End If
        Next j
    Next i
    SortArray = a
End Function