Creating a Custom Field that increments

Just wanted to run this by for thought.

Customer wants to print a form, say an invoice, and have it automatically increment a Reference # field.   This reference # is the date plus an A, B, C, etc.  It would go on each invoice printed and increment each invoice

Example on today, 1/12/23 the first invoice would have Ref# 01122023A , then next would have Ref#  01122023B, and so on.

Is this achievable with a script and custom field - store the current date in that format, and the script to increment in some way?

Thanks for any suggestions (or denials)