I'm aiming to produce two solutions, one with pivot tables and one with just formulae. This will allow comparison and if they're the same all well and good, you'll have a choice. If they're different then some detective work will be needed.
p45cal
Everyone: If I've helped and you can't be bothered to acknowledge it, I can't be bothered to look at further posts from you.
If OB AHT = "" or 0, the value of Full AHT is IB AHT/IB Tasks
Otherwise, the formula is IB AHT + (OB AHT *(OB TASKS/IB TASKS))