Converting a "Logged out" time and "logged in" time to find out the elapsed time
 

I am a manager in a big office where agents log into their phones to
get calls. We keep track of how many minutes an agent is "logged off"
of their phone system. I would like to be able to have a formula to
use in Excel to speed up the calculations for this info. Here is what
the info looks like that I am given and what I need to calculate:

Sunday, December 03, 2006
Agent Login Time Logout Time # of minutes
logged out
Doe, Jane 6:58am 8:51am (need to
find # minutes from 9:39am-8:51am)
Doe, Jane 9:39am 2:30pm (need to
find # minutes from 2:30pm-2:34pm)
Doe, Jane 2:34pm 3:29pm (need to
find # minutes from 3:29pm-4:15pm)
Doe, Jane 4:15pm 5:00pm

I cannot seem to get a formula to work that will calculate the time
difference in minutes. Can someone help????