Dear Gentlemen

I need a formula that will let me determine the maximum amount of
simultaneous calls in a 24 hour period, what I have is:

Call started at Duration
03/03/2009 09:44:57 00:00:40
03/03/2009 09:38:32 00:00:22
03/03/2009 09:37:13 00:02:46
03/03/2009 09:35:39 00:01:28
03/03/2009 09:35:32 00:00:49
03/03/2009 09:34:31 00:00:17
03/03/2009 09:33:26 00:00:51
03/03/2009 09:31:48 00:00:25
03/03/2009 09:31:01 00:01:29
03/03/2009 09:27:29 00:00:49
03/03/2009 09:26:29 00:00:31
03/03/2009 09:24:00 00:15:04

In this case the maximum of simultaneous calls is 3, but I need a formula
that will give me the answer.

I'm kind of new to excel, so help will be greatly appreciated.

Thanks & regards
farid2001