Test A Random Number For Nearby Numbers

not after code, just thoughts, suppose i'm generating a random 8-digit pin number for our clients, first i'll be checking against the db to see if it already exists before assigning it. what i might do for that is getstring all of the exsiting pins at the top of the script and just keep performing an instr until i get a 0. (i dont expect to ever go above a thousand clients for this system and hopefully my initial number will be random enough that these checks are for backup/redundancy assertion anyway)

but anyway, the main problem is: i dont want to generate a random pin that is one (or maybe two) digit(s) different from another,. i.e.

11111111 is too close to 14115111 and much too close to 11111811. 11121111 is right out of the question as it can be entered as a typo, as is 11111411 because of the numpad

so i'm after thoughts on how to perform that check, i suppose if i went with the "big string of all pins that went before" check i could perform a number of regex searches on the string. i.e.

my pin is 12345678 and i dont want ony to be one digit different so i'd check the string against .2345678 1.345678 12.45678 and so on. think i just answered my own question, anyone else got any ideas? especially for the two digit case (dont want to be performing 36 regex checks do i!)