You have been doing your research! Good to see.
Well, I've been educated also! But I wonder if the use of SUMIF, SUMIFS OR SUMPRODUCTS would do the task also. There's a homework exercise for you.
Maybe create a copy of your work book and try the SUMIF, SUMIFS OR SUMPRODUCT formulae. You can use named ranges in those types of functions. But then again, if your original formulae still work, why bother? It may be best to just understand them and file that understanding to the back of your mind.
Anyway, thanks for supplying the various links. It was interesting reading (I know, I need to get a life!).
Good hunting Quarterp!