adding items to a Listview problem

I wrote a program that manages serial keys, writes them to the registry in a strong encryption and reads them back etc.  When I add an application to the listview, the first two go alright then each one I add afterwords makes one additional entry (2, then 3 etc).  Below is the code when the add button is clicked:

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    Private Sub add_application()
        Dim i As Integer
        Try
            If appNameBox.Text = Nothing Then
                MsgBox("Please enter an application name", MsgBoxStyle.OKOnly, "Missing Name")
                appNameBox.Focus()
                Exit Sub
            ElseIf appSerialBox.Text = Nothing Then
                MsgBox("Please enter a serial key", MsgBoxStyle.OKOnly, "Missing Serial")
                appSerialBox.Focus()
                Exit Sub
            Else
                apName = appNameBox.Text
                apSerial = appSerialBox.Text
                existing_application()
            End If
            appNameBox.Text = Nothing : appSerialBox.Text = Nothing
        Catch ex As Exception

            MsgBox(ex.ToString)

        End Try
        saved = False
    End Sub

 Private Sub existing_application()
        ''weird..
        Dim lvi As ListViewItem
        If Not appList.Items.Count = 0 Then
            ' For i = 0 To appList.Items.Count - 1
            For Each lvi In appList.Items
                If apName = appList.Items.Item(i).Text Then
                    Select Case MsgBox("Previous entry found.  Update it?", MsgBoxStyle.YesNo, "Update Entry")
                        Case MsgBoxResult.Yes
                            Dim item As New ListViewItem
                            item.Text = apName
                            item.SubItems.Add(apSerial)
                            appList.Items.Item(i).Selected = True
                            appList.Items.Remove(appList.SelectedItems.Item(0))
                            appList.Items.Add(item)
                            Exit Sub
                        Case MsgBoxResult.No
                            Exit Sub
                    End Select
                Else
                    Dim item As New ListViewItem
                    item.Text = apName
                    item.SubItems.Add(apSerial)
                    appList.Items.Add(item)
                End If
            Next
        Else
            Dim item As New ListViewItem
            item.Text = apName
            item.SubItems.Add(apSerial)
            appList.Items.Add(item)
        End If
        saved = False
    End Sub

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What did I do wrong?