how do I open a version controlled spreadsheet on SharePoint?

All,
If I try to open an excel workbook on SharePoint from a Document Folder that does not have Version Control, it works fine.
I am using this simple code:

Public Const RESOURCE_FILE_LOCATION = _
    "http://path.to.real.file/filename.xlsx"
Sub test()
    Dim msg As String
    On Error GoTo Oops:
    Workbooks.Open Filename:=RESOURCE_FILE_LOCATION
    On Error GoTo 0
    Exit Sub
Oops:
    If Err.Number <> 0 Then
        msg = "Error # " & Str(Err.Number) & " was generated by " _
            & Err.Source & Chr(13) & "Error Line: " & Erl & Chr(13) & Err.Description
        MsgBox msg, , "Error", Err.HelpFile, Err.HelpContext
    End If
End Sub

However when I try to do it from a folder that has revision control, I get Error #1004. However the path does exist, the file is not being used by another program and I am not tying to save the workbook. If I click the file location in SharePoint, SharePoint asks me if I want to open the file as read only, or check the file out and edit it. For the purposes of my program, read only is fine.

I have also tried adding Readonly:=True to the open line like this:

    Workbooks.Open Filename:=RESOURCE_FILE_LOCATION, ReadOnly:=True

but that does not work either.
Suggestions?
Thanks