Option Explicit
Sub RemoveDuplicates()
Dim AllCells As Range, Cell As Range
Dim NoDupes As New Collection
Dim i As Integer, j As Integer
Dim Swap1, Swap2, Item
Range("A1:A15").Select
Set AllCells = Selection.SpecialCells(xlCellTypeVisible)
On Error Resume Next
For Each Cell In AllCells
NoDupes.Add Cell.Value, CStr(Cell.Value)
Next Cell
On Error GoTo 0
For i = 1 To NoDupes.Count - 1
For j = i + 1 To NoDupes.Count
If NoDupes(i) > NoDupes(j) Then
Swap1 = NoDupes(i)
Swap2 = NoDupes(j)
NoDupes.Add Swap1, before:=j
NoDupes.Add Swap2, before:=i
NoDupes.Remove i + 1
NoDupes.Remove j + 1
End If
Next j
Next i
For Each Item In NoDupes
UserForm1.ComboBox1.AddItem Item
Next Item
UserForm1.Show
End Sub