Help, a query i am not able now to solve!

[palouf]

Hello,
I hope you will be able to help me.
I want to do te following operation:

i have one table : APP
Id_app
with
Name
Start time
Start Date
Stop Time
Stop Date
Duration
User

so for example i would have:
APP:
IExplore 10:00:00 12/07/03 11:00:00 12/07/03 1 hour(s) 0
Minute(s) 0 second(s) 2
IExplore 10:20:00 12/07/03 10:45:00 12/07/03 0 hour(s) 25
Minute(s) 0 second(s) 2
IExplore 10:50:00 12/07/03 11:10:00 12/07/03 0 hour(s) 20
Minute(s) 0 second(s) 2
IExplore 8:00:00 12/07/03 10:00:00 12/07/03 2 hour(s) 0
Minute(s) 0 second(s) 1
IExplore 9:20:00 12/07/03 10:25:00 12/07/03 1 hour(s) 5
Minute(s) 0 second(s) 1
IExplore 10:30:00 12/07/03 14:10:00 12/07/03 3 hour(s) 40
Minute(s) 0 second(s) 1
IExplore 10:30:00 13/07/03 10:43:00 13/07/03 0 hour(s) 13
Minute(s) 0 second(s) 1
and i would like to obtain the total time of use of Iexplore :
so smthing like that :
IExplore 10:00:00 12/07/03 11:10:00 12/07/03 1 hour(s) 10
Minute(s) 0 second(s) 2
IExplore 8:00:00 12/07/03 14:10:00 12/07/03 6 hour(s) 5
Minute(s) 0 second(s) 1
IExplore 10:30:00 13/07/03 10:43:00 13/07/03 0 hour(s) 13
Minute(s) 0 second(s) 1

So i can suppose a "group by user, start date" at the end,
i can also feel a Start time : min Start Time
Start date : min Start date
Stop time : max Stop Time
Stop date : max Stop date
i have only iexplore in the app list, so no need to sort with this field

BUT Duration is my problem, as you can see, 2 iexplorer can be
opened at the same moment, and i shouldnt count them both but only the Real
duration

Thanks For your help. or even only having thought about it

Pascal