[SL] Incrementing, Resetting invoice numbers?

[Luke <sl...@li...>]

This is a "how to" question.

Currently, we have our invoice, etc., numbers in defaults, setup like 
this:

<%yy%><%mm%>-01

So, the first invoice of 2008, for example, would be:

0801-01

The second would be:

0801-02

Assuming we do not generate any more invoices in January, and do the next 
one in February (in other words: a failing business:)), the next invoice 
would be numbered:

0802-03

That last number keeps increasing, and never resets.  I would think that 
there should be a way to make it automatically reset when the base number 
(in this case the year/month combo) changes.
In other words, I want that first February invoice to be numbered:

0802-01

Is there any way to make this happen?

Thanks and regards,

Luke