title: How do I track who uses my Excel spreadsheet?
body: <p>I created an Excel spreadsheet that my boss wants to put on the company's internal website.  The spreadsheet contains some seldom-used, esoteric, but handy functions that only certain employees within the company will find really useful.  </p>
  
  <p>The problem is that I don't know who the future users are, and my boss wants me to identify who uses my spreadsheet.</p>
  
  <p>He asked that I password-protect the Excel spreadsheet in such a way that one password does NOT unlock all of the copies that people can download from the site.  For example, I can't just make the password "stackoverflow" because once a user legitimately gets the password from me, and is shared with other people, it can be used by anyone within the company to unlock all subsequently downloaded spreadsheets. I will never be able to ascertain who is using the spreadsheet.  Also, I cannot modify the website, so I hope to achieve this tracking of users through Excel and email.  </p>
  
  <p>Is there a way to have Excel randomly generate a string, which the user emails me, and then I respond with the appropriate password that will unlock the file (based off the generated string)?  This requires the user to check in with me before using the spreadsheet (the ideal situation).  </p>
  
  <p>Is such an arrangement possible in Excel 2010 Professional Plus?</p>