title: Uniquely identify users in shared workbook without updating
body: <p>I have a shared workbook in which there are two main tabs. One is a worklist and one is a hidden Ongoing sheet. When a row in the worklist is updated (or the last 3 or 4 cells), there's a range change event that automatically copies that data to the Ongoing sheet. So the worklist is the current status of everything and the Ongoing is the full history (a pivot table is used to show the full history when required).</p>
  <p>This all works fine, except when multiple users have it open. They overwrite each other on the Ongoing sheet. To get round this, I used GetUserName, so each user would 'post' to a different range on Ongoing - I'd post to rows 1000 onwards, a colleague to 2000 onwards and so on. It gets around the issue of writing to the same rows.</p>
  <p>I have the GetUserName populating a cell so I can see it. When I have the workbook open, it shows mine but, when someone else opens it, the getusername is updated with their details in <em>my</em> version as well.</p>
  <p>I need each open instance to keep a reference themselves so they continue to post to a different row. I don't necessarily need GetUserName if something else works, but it needs to be something that won't overwrite the variable for all users. A way to identify all users individually when they have the sheet open.</p>
  <p>Can you help?</p>