a Challenge for me

dear friends i have a problem that i can't sort it out though i have tried
alot anyhow i am here to get help from you people the problem i have is

suppose if i have a serial of numbers and if i sell a particular serial out
of that so i want to know that which serial is in my hand for example

if i have serial from 1 to hundred and i sell number 88 so i want to know
that number 88 is no more availabe in the whole serial as it is sold out .

Note : i will be thankful if you people sort it out or give an ultinative
suggestion or solution for it thankx