1) Is it a true statement that Iteration is only relevant to allowing or
disallowing Excel to try and calculate a solution to circular reference
errors? (I have a co-worker who seems to think that if a workbook contains
VBA code where there is a loop, you need to turn Iteration on.)

2) Is this an Excel-wide setting, or does it pertain to a particular
workbook? It seems to me that if I alter the Iteration settings in a workbook
(i.e., turn iteration off), if I close that workbook and open a new one, it
turns Iteration back on.

3) It also seems like the Excel default is Iteration on, 10 max attempts. Is
that true? Is there a way to change the default?

TIA
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Hmm...they have the Internet on COMPUTERS now!