Trying to open Excel 2003 file in ReadOnly mode based on condition

Hello, I'm very new to VBA. This was easy enough to do in Word, but after trying to convert this to do the same thing in excel, I'm having trouble. I am Trying to open Excel 2003 file in ReadOnly mode based on condition. Here is what I have so far,

I am getting a Compile error "Method or data member not found on the Module at '.xlApp' and then I am getting another error when I try to access the "ActiveWorkbook.FullName" - Any help would be appriciated. thx

This Workbook:
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Public Sub Workbook_Open()
   SetAutoOpen
End Sub

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Module:
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Option Explicit
Dim objAppClass As New ClassModule01
Public FirstNewXL As Boolean
Public oldNoOfOpenXL As Long

Public Sub SetAutoOpen()
    Set objAppClass.xlApp = Excel.Application
    oldNoOfOpenXL = 0
    FirstNewXL = True
End Sub


Class Module
===================================================
Private WithEvents xlApp As Excel.Application

Private Sub xlApp_NewWorkbook(ByVal Wb As Workbook)
    Dim thefilepath As String
    thefilepath = ActiveWorkbook.FullName
    If InStr(1, thefilepath, "Temporary Internet", vbTextCompare) Then
        ActiveWorkbook.Close
        Workbooks.Open Filename:=thefilepath, ReadOnly:=True
    End If
End Sub