Back to your original post:

a) identify a starting and ending point.... Excel can find anything it's asked to find if it exists. It's the user that must tell Excel what it's to look for or how to identify whatever it's looking for.

That's the part of your problem that's missing. I think your last post says that within each NEWCASE there are audit notes that would "pair up" to give start and end of tasks, but without Excel knowing this, no time taken can be calculated.

b) insert a row after the end point..... first you need to solve the identity problem then it's just a matter of .Offset(1, 0).EntireRow.Insert

c) calculate the time between start and end point. There is a further problem in that tasks started and completed overnight show as an error.... For cell C13 of your posted sheet the Time Taken =(B12+C12)-(B3+C3) formatted [h]:mm:ss