Excel: check if cell contains only alphanumeric

https://www.techonthenet.com/excel/formulas/alphanumeric.php


http://stackoverflow.com/questions/29149916/formula-to-eliminate-all-but-alpha-characters


http://stackoverflow.com/questions/15723672/how-to-remove-all-non-alphanumeric-characters-from-a-string-except-period-and-sp