Here's a small routine to show what I'm talking about. If you define your Times such that the Date is included.
You will not have the issues you have currently.
When you record the CallStart you can use Now to assign the date and Time to CallStart. And when you record CallCleared you use Now to assign the date and Time to CallCleared.
Code:
Sub MilitaryTime()
Dim CallStart As Date 'General Date format
Dim CallClearedAt As Date 'General Date format
'Simulate a time today and a time just after midnight
CallStart = #2/21/2013 11:50:00 PM# '
CallClearedAt = #2/22/2013 12:03:25 AM#
'
'Get the difference in seconds, then divide by 60 to have result in minutes.
Debug.Print DateDiff("s", CallStart, CallClearedAt) / 60 & " minutes"
End Sub
Good luck.