Stamping or Bates Numbering

I've got a series of pages with the following Bates number:
 
MM/DD/YY - 000284(a).
 
I would like to know if its possible to "increment" the alphabetic character while keeping the number (000284) the same.
 
So, the sequence would look like:
 
MM/DD/YY - 000284(a)
MM/DD/YY - 000284(b)
MM/DD/YY - 000284(c), and so on.
 
Any help would be greatly appreciated.
 
Thank you.