[O] Scheduling a meeting every week for a given time

[Claude Fuhrer]

Hi

I'm trying to add recurring events, but only for a given period of time. 
For example, I would like to write:

Project meeting,  every monday between 10:00 and 12:00 from 1. October 
until 1. December 2015

or

Staff conference, every friday from 15:00 to 17:00, during seven weeks

I've tried something like:

*** Project meeting             
    DEADLINE: <2015-09-07 lun 12:45-14:20 +1w>--<2015-10-19 lun>    

But this event then appear every in my agenda. What is the good syntax 
for that ?

Thank you for your help