Unique Code Generation

I am looking for a webpage, where the source can not be seen, and the following criteria happen. 1.) User clicks a link to generate a code (opens your page you are creating) 2.) The code is generated based on the following formula 3.) First 4 digits are hard coded – I need to be able to set this at anytime 4.) Next 6 digits are sequential starting with 000010 – I need to be able to set the starting value at anytime 5.) Next 4 digits are hard coded – I need to be able to set this at anytime 6.) Last digit is calculated a. If the last number in step 4 is not a zero, this number increases by 7 b. If the last number is a zero, this number increases by 6 Basically, I need to be able to set the starting number and the code will pick up from that number I set. Example: xxxx000010xxxx0 xxxx000011xxxx7 xxxx000012xxxx4 xxxx000013xxxx1 xxxx000014xxxx8 xxxx000015xxxx5 xxxx000016xxxx2 xxxx000017xxxx9 xxxx000018xxxx6 xxxx000019xxxx3 xxxx000020xxxx9 – Since the number switched to a zero (20) , it only increased the last number by 6 xxxx000021xxxx6 The user should only be able to generate 5 unique codes. Once they have generated 5 codes, it would then say “You have generated all the codes you can” The sequence must be continuous no matter who the user is. Meaning the same sequence will never be displayed twice. Once it is generated by 1 user, the same sequence will not be generated by another user. So if there are 5 users clicking the link, each will receive the next number in the sequence, never will they receive the same. The output displayed on the page should be something like: “Your uniquely generated code is “xxxxxxxxxxxxxxx” “This code expires on June 24, 2016”