title: Report - Running Count within a Group
body: <p>I have an Access 2007 report which is grouped by RoomType_ID</p>
  
  <p>I need to do a running count on each line within the Group so that I end up with something like:</p>
  
  <p>RoomType_ID 1
  1  Mr and Mrs Smith
  2  Mr and Mrs Jones
  3  Mr and Mrs Smythe</p>
  
  <p>RoomType_ID 2
  1  Mr Foo
  2  Mrs Bar</p>
  
  <p>etc...</p>
  
  <p>How can I go about getting this?</p>