Private Sub UserForm_Initialize()
Me.ComboBox1.List = Application.Transpose([A1].CurrentRegion.Resize(1))
End Sub
Private Sub ComboBox1_Change()
[A1].CurrentRegion.Sort Key1:=[A1].Offset(, Me.ComboBox1.ListIndex), Header:=xlGuess
End Sub
Private Sub Workbook_Open()
UserForm1.Show
End Sub