calcluating difference in time

[kurt_n]

Please someone help me with this.

We are calculating the uptime/downtime of a system. we have the following data

start time end time
10:20 10:40
10:30 10:50
10:20 10:30

The difference in first column is 20 minutes, 20 in 2nd line and 20 in third line.
WE need to calcluate the total downtime for a week. in the above example, if we take the difference in all the tree, it should come to 60 minutes which is not true.
Since the third row lies between duration of downtime of first row, it should be neglected. So the total downtime actually is 40 minutes including first and second row.
I need to calculate this using a formula.
Can anyone help me in this?

Thanks in advance
kurt

[Mikeopolo]

Perhaps this will work:

First sort the data on start and end columns.
Then add column D as cumulative
Then in these cells type:
D2: =c2 (ie first row is always correct)
D3: =IF(A3>=B2,C3,MAX(B3-B2,0))
Copy D3 down to the end of the table.
Add column D for the total for the period.

Regards
Mike

[kurt_n]

thanks a lot Mike.
I will try this and will let you know the result.