Need help in calculating downtime

Hi...


I am using excel to calculate my equipment downtime with parameters like locationwise equipmentwise and want to summarize that on monthly basis

Sheet 1

Fault Reported Fault Resolved ]
Date Time Date Time Mins Response Time [Day:Hour:Min:Sec] Location
01 April 2013 11:00 Lane 01 29 April 2013 13:00 40440 28:02:00:00
01 April 2013 11:00 Lane 01 29 April 2013 13:00 40440 28:02:00:00

For mins cloumn i used below formula to calculate mins
=(((I7+J7)-(C7+D7))*24)*60
and then days hours and mins by using below formula
=(N7/24)/60 Format used d\:hh:mm:ss

Till here it works well.
Sheet 2

Location April-13
Days [Day:Hour:Min:Sec]
Lane 01 25:04:00:00
Lane 02 0:00:00:00
But suppose if i have a downtime in sheet 1 eg. 28,28 days for any two days or more here it doesn't give accurate results

in sheet i have used =SUMIF('Apr-13'!$G$7:$G$150,$A4,'Apr-13'!$O$7:$O$150) as i have to summarize monthly downtime which may be in many days..


Please can any one help me...

pls can anyone help me on th attached sheet...