Hi Martinique,

I think if you generated a report  using "Course Completion" under the Source dropdown box in the New Report section it may be possible to get the results you're after.

If you edit the columns so that you have a combination of "Completion Status", Completion Date", "Date Started", "Course Start Date" and "Date enrolled" you should be able to produce a report which you can manipulate in Excel (using the COUNT function) to produce your answer. 

regards,

George.