title: Unique excel workbook identifier in vsto
body: <p>I'm busy with a .net excel vsto addin and came across the issue of the ribbon being "shared" across multiple instances of excel. I got past that by assigning a unique identifier to the custom document properties when the document loads and no key exists. This works fine. </p>
  
  <p>I then use this unique identifier to save / load ribbon settings for the specific workbook. These keys and settings are then saved against the unique identifier in a SQL express localdb. Still fine. </p>
  
  <p>The problem is now that in the event of someone duplicating the excel document both these documents obviously then have the same identifier in the document properties which in turn causes updates in both document to update the same settings in the database. </p>
  
  <p>I've searched, and it seems the answer is no, but is there any unique key/name/field/code that I can use that is unique between files / workbooks?</p>