I'm working on a database that was originally coded to output a .xls Excel file. We need to change it to .xlsx, but I can't figure it out. I tried simply changing ".xls" to ".xlsx" but that didn't work. It generated an error on the `Set wbk= XLapp.Workbooks.Open(SavePath).Sheets(1)` line--at least that's what the debugger highlighted. Here's the current code section:

```vb
Private Sub ExcelFeederReview_Click()
Dim SavePath As String
SavePath = fGetMyDocsPath & "\FeederReview_" & Format(Now, "YYYYMMDD_hhnn") & ".xls"
'Run Query and export to Savepath
DoCmd.TransferSpreadsheet acExport, acSpreadsheetTypeExcel9, "qFeederExport", SavePath, False, "FeederReview"

'Open query in excel shell
Set XLapp = New Excel.Application
Set wbk = XLapp.Workbooks.Open(SavePath).Sheets(1)

'Format excel doc with excel shell
    With XLapp
            .Application.DisplayAlerts = False
            .Application.Rows("1:1").Select
            .Application.Selection.Font.Bold = True
            .Application.Selection.Orientation = 90
            .Application.Selection.Interior.ColorIndex = 15
            .Application.Range("A2").Select
            .Application.ActiveWindow.FreezePanes = True
            .Application.Range("A1").Select
            .Application.Selection.RowHeight = 86
            .Application.Columns("D:D").Select
            .Application.Selection.NumberFormat = "###0.00"
            .Application.Cells.Select
            .Application.Selection.Font.Name = "Arial"
            .Application.Selection.Columns.AutoFit
            .Application.Range("A1").Select
            .Application.ActiveWorkbook.SaveAs FileName:=SavePath
            .Application.ActiveWorkbook.Close
            .Quit
    End With

'Allows user to view and open file
    OpenFileDiag = MsgBox("Feeder review file saved to the the following location:" & vbCrLf & vbCrLf & SavePath & vbCrLf & vbCrLf & "Would you like to view Saved File?", vbYesNo, "View Saved File?")

'Yes selection opens saved formated excel file
    If OpenFileDiag = vbYes Then

        Set XLAppOpenToView = New Excel.Application
            XLAppOpenToView.Visible = True
            XLAppOpenToView.Workbooks.Open SavePath

'No selection unloads excel shell
    ElseIf OpenFileDiag = vbNo Then

            XLapp.Quit
            Set XLapp = Nothing
            Set XLsheet = Nothing

        Exit Sub

    End If
'Unloading of excel shell to prevent multiple open excel instances
    XLapp.Quit
    Set XLapp = Nothing
    Set XLsheet = Nothing

End Sub

```