That should be pretty simple. Your query would be something like:
SELECT * FROM $my_table WHERE date_field = "04/20/2002" OR date_field = "04/19/2002";
This assumes that today is 4/21/02, of course.
If you want to make this dynamic, then you will have to get the current date (see time functions in library) and subtract one and two days from it, and then run the query.
Then you could use something like:
WHERE date_field < $today AND date_field > $three_days_ago;
