Open xlsx in Office 2003

[Viensterrr]

I got a VSTO addin which attaches to the Open event. I have installed the Office 2007 Compatibility Pack for office 2003, and then tried to open an xlsx file. In the open even handler, I am getting a workbook passed in but with unexpected parameters. The filename is of the form "CVT5CB.tmp" and the location is the Temp folder. I have also tried with a Shared Add-in and it has the same issue. So I dont know whether this is a problem with VSTO or the addin. Can anyone tell me whether this is a bug in Office Compatibility Pack? Please let me know how to solve this issue? Thanks.

[Delil]

It is not at all possible. You have to upgrade Office to 2007 to run the most latest file format. Or else it just a waste of time. It is necessary that you must upgrade. Any Office 2007 format does not work on Office 2003. The most you can do is simply download a Office 2007 file viewer that will allow you to see the files only. There is no way to modify it.