Patrick,

Thanks for your comment.

I am slowly coming to the conclusion that I might as well rewrite my
AddIn for Word 2007 using Visual Studio Tools for Office. This way I
should end up with a much more neat and future proof solution (albeit
one that will only work in Office 2007).

If I am going for a rewrite then I think that a better solution to my
problem is to intercept the DocumentBeforeSave event and use the
ChangeFileOpenDirectory to set the path. However, I need to do a
similar thing with FileOpen so repurpopsing the FileOpen command seems
to be a good idea. I've created a new Word 2007 addin using VSTO 2005
SE and repurposed the command and it works perfectly! I can even slip
in my ChangeFileOpenDirectory command and let Word show the open
dialog itself!

For information, here is my RibbonX and my callback function.

<customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui"
onLoad="OnLoad">
 <commands>
   <command idMso="FileOpen" onAction="OnFileOpen"/>
 </commands>
</customUI>

public void OnFileOpen(Office.IRibbonControl control, ref bool
CancelDefault)
{
       string path = GetPath();  // Ask the user a question to
determine the path
       if (path!="")
       {
               addin.Application.ChangeFileOpenDirectory(path);
       }
       CancelDefault = false;  // Do NOT cancel the default behaviour
}

Dave