I am faced with the need to create (actually participate with) an alphabetic numbering system. The sequence is straight forward, and looks like this:

AAAA
AAAB
.
.
AAAZ
AABA

etc.

Really my only need is to be able to increment these codes by one, so I need a function that receives "DPRZ" and returns "DPSA". Get it?

I am fairly confident that I can pound out the code to do this, but all of my ideas so far would take an enormous amount of code- can anybody think of a practical solution?