I assume you are using Date parameters in your select statement to filter the dates.
That will supercede any join you do (and exclude peopel that do not have any recorsds in that date range).
You could not filter on the dates,
group on the employee
Suppress details that do not fall in your date range
create a formula field for hours (if date in ?startdate to ?enddate then hoursfield else 0) and SUM it per employee or use a RT to only count those records.
Edited by DBlank - 08 Dec 2009 at 12:19pm