Do you just need code to generate the strings in that sequence or do you need conversion to/from int?
The implementations likely will be quite different depending on the answer.
(Code based on the code you've posted assumes all you need is the strings in sequence. And never needing to start mid-sequence!)
It could be that is what Angela (OP) wants, however what is shown is that after Z9999 is AA000. I.e., as the length of the alpha part of the string gets longer, the numeric part gets shorter. The total string length remains 5.
Last Visit: 31-Dec-99 18:00 Last Update: 24-Oct-14 9:26