finding weekly hours

Hi

I have a data in excel2003.There is a 6 months data which shows employees office starttimes and endtimes.There are 3 coloumns as follows
date startime endtime
01/04/2011 09:20 18:40
01/05/2011 09:31 18:45
01/06/2011 09:35 18:43
01/07/2011 09:29 18:41
01/08/2011
01/09/2011
01/10/2011 09:27 18:37
01/11/2011 09:45 18:41
01/12/2011 09:27 18:44
01/13/2011 09:28 18:40
01/14/2011 09:29 18:42

i want to find Weekly working hours for every week.Can anybody help me.Thanks in advance

Regards,
Rawindar

Hi
see the attached file

Sadath