Erm.. I guess the above would ALSO mean limiting the user-input to 3 at a minimum, but you might also let them enter 1 or 2 and use that info to determine just "how far" outside of the tolerance value to look for the total of 3 :).  (ie. if they input 1, maybe just double the tolerance range. If they input 2, then tripple it and if they input >= 3, quadruple it, etc.).

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