how to handle schema changes?

So, I wrote a quick vqmod extension that let's you manage a manufacturer wholesale price and manufacturer part number for products (for profit reporting and reordering purposes), but it requires 2 fields be added to the product table. What's the "official" way to do a database schema change with vqmod extensions? once I have that, I'll be able to post this in the free section of opencart.com, I think.

Just saw this question posted in the concept section here:

http://forum.opencart.com/viewtopic.php?f=24&t=52759