Last updated: before December, 1998
For the previous week (Sun - Sat): ('date'= your date field)
if(weekofyear(date)=weekofyear(today())-1 and
year(date)=year(today()))
If the data is only for one year, then you can leave out the 'and' and all that follows.
For the last 7 days: (including today)
>=@TODAY()&<=@TODAY()+7
Or, if you need to find records produced during the last 7 days:
... starting with and including today's date, use the formula:
>=@TODAY()&<=@TODAY()+7