Different results for ComboBox.RowSource property in BeforeUpdate Event

Greetings,

I have the following code in the beforeupdate event of combobox.

Private Sub ComboBox1_BeforeUpdate(ByVal Cancel As MSForms.ReturnBoolean)

'-----------------------------------------------------------------------------------
'Adapted: http://www.excelforum.com/excel-programming/661182
          '-update-a-combo-box-list-which-list-is-on-a-different-worksheet.html
'-----------------------------------------------------------------------------------

'If new sector is entered, add to combobox drop-down list
If WorksheetFunction.CountIf(Range("test"), ComboBox1.Value) = 0 Then
    With Range("test")
        If .Rows.Count = 1 Then
            .Offset(.Row) = ComboBox1.Value
        Else
            .End(xlDown).Offset(1) = ComboBox1.Value
        End If
        .Sort .Cells(1)
        ComboBox1.RowSource = .Parent.Name & "!" & .Address
    End With
End If

End Sub

While debugging, I noticed that the line result for

ComboBox1.RowSource = .Parent.Name & "!" & .Address

is different from

ComboBox1.RowSource = .Parent.Name & "!" & Range("test").Address

The former is always one row less than the latter. Can someone please explain what could be the cause even though I have a WITH statement to identify the range?

Many thanks
Asha