Aladin Akyurek wrote...
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[1] The SumProduct function should implicitly coerce the truth values to
their Excel numeric equivalents.
[2] The lookup functions should have an optional argument for the return
value, defaulting to #N/A in its absence.

Interesting signature, but the first would require SUMPRODUCT to work
differently than other functions with respect to boolean TRUE. If you
want that functionality, you could always switch to Gnumeric.

As for the second, it'd be nice if there were an error trapping
function or even better a general trapping function: a function that
would return the value of its 1st argument if it satisfied its 2nd
COUNTIF/SUMIF-like criteria argument or the value of its optional 3rd
argument otherwise, with the default value for the 3rd argument being
VBA Empty, so "" in text contexts or 0 in numeric contexts.

Still, I'd prefer eliminating the artificial 7 nested function call
limit and allow different files with the same base filename to be open
at the same time, no matter how much recoding would be necessary.