C# - This operation cannot be performed in this event handler.

I am getting this error:
Presentation (unknown member) : Invalid request.  This operation cannot be performed in this event handler.

I am trying to close an instance of power point from within an add-in.

Basically I open another file by launching internet explorer and providing a ulr that points to another powerpoint presentation.  This works well.

After I do that I just want to close the program that I am in, but I get the error.

Even without opening the other file, how can I just shutdown powerpoint from an add-in, that is my real problem.

        void Application_PresentationOpen(Microsoft.Office.Interop.PowerPoint.Presentation Pres)
        {
                            Process.Start("IExplore.exe", rnetlocation);
                            Globals.ThisAddIn.Application.ActivePresentation.Close();