Hi, I had perpared a report to show the overtime work and time off balance of staff. the report like this: (the total_min column will not show in the report, it just a field in dataset) From To No. of hours Balance total_min 01/01/2011 12:00 01/01/2011 17:00 7 hr 0 min 7 hr 0 min 420 07/03/2011 12:00 09/03/2011 14:00 ( 2 hr 0 min ) 5 hr 0 min -120 07/03/2011 19:00 09/03/2011 20:30 1 hr 30 min 6 hr 30 min 90 10/03/2011 17:00 10/03/2011 17:30 ( 0 hr 30 min ) 6 hr 0 min -30 I have no idea how to set expression in reportviewer to calculate the "Balance" column in each row that it will sum the value of previous row ? ( i already had a 'toal_min' column in dataset which can use for calculation) Thanks. Joe

Try the RunningValue function: http://msdn.microsoft.com/en-us/library/ms159136.aspx =RunningValue(Fields!NoOfHours.Value, Sum, Nothing) You will need to convert number of hours to a decimal or something that can be totalled.Russel Loski, MCT