riskiana 0 Newbie Poster

Hi, can u help me? i've got problems.
this is my table:
No Status Date/Time Aging
1 registerd 2010-06-21 11:44:51 0 hours
2 in progress 2010-06-24 12:39:12 40 hours
3 closed 2010-06-24 12:40:18 40 hours(total aging)

how to get aging if time count only at 08.00 until 21.00 and only workdays(except saturday and sunday).
example at this table: aging 40 hours is got from between 2010-06-24 12:39:12 and 2010-06-21 11:44:51
thanx :)