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SUBMIT YOUR IDEAjust a single iterative macro
Did this as per the question by finding the first prime number <= number entered.
This made me go back to my college math theory class (although I had to look up the formula online). Standard macro is only to keep as a nice package - iterative macro inside it does the real work. I limited it to a maximum test number of 100K as the larger the number the exponentially longer the macro takes to run. The standard macro also includes a Test tool in case the iterative macro hits the iteration limit before calculating all primes (won't happen the way with limit at 100K).
Workflow:
Macros: