Useform on change modify code by ComboBox2 YES/NO entry

I have a userform which searches a database of numbered entries, returning all instances of the search word in textbox6 from two columns of the database.

The final control will be ComboBox2 (a YES NO choice)

If YES the code is to remove entries from the retrieved listings that begin with "20" only

If NO the code is to remove entries from the retrieved listings that begin with "19" only

How can I adapt the following

Private Sub TextBox6_Change()
    Dim a, i As Long, w(), n As Long
    Me.ListBox4.Clear
    If Me.TextBox6.Value = "" Then Exit Sub
    a = Sheets("ewccodes").Cells(1).CurrentRegion.Value
    For i = 2 To UBound(a, 1)
        If UCase$(a(i, 3)) Like "*" & UCase$(Me.TextBox6.Value) & "*" Or UCase$(a(i, 4)) Like "*" & UCase$(Me.TextBox6.Value) & "*" Then
            n = n + 1
            ReDim Preserve w(1 To UBound(a, 2), 1 To n)
            For ii = 1 To UBound(a, 2)
                w(ii, n) = a(i, ii)
            Next
        End If
    Next

    If n > 0 Then Me.ListBox4.Column = w

End Sub

Any help appreciated