Hi Ibrahim,
There is a way: It's called the Scheduler module:
http://docs.moodle.org/20/en/Scheduler_module
http://moodle.org/plugins/view.php?plugin=mod_scheduler
I haven't tried it myself but it may be better than the standard calendar. The Moodle Calendar isn't smart in that it doesn't recognise if there are overlaps (i.e. double-bookings). I do like the ability to export to iCal though, that's very handy.