The MLS search gui is crappy but it can be done. In essence the way that sdrealtor creates the short sale monitor would be the way to do it. You choose a zip code, search for sold properties and put in keywords such as REO, short, corporate owned, in the remarks or confidential remarks section. It is pretty manual. It works great for the short sale monitor as sdr does the whole county and as he says, the exact numbers are not as important as the trendlines that are used for analysis.
A much more nifty way to do it would be to have a script that parses through assessors records to capture all of the sellers. Then process that database for keyword names that are banks, lenders etc….
I would bet there are plenty of software guys who monitor this site that could generate that sort of code.