>> "have you been in the United Stated during the last 90 days"? and two check boxes conveniently marked yes and no. How would you model that? <<

They don't care about your trips to AIDS infected Africa? Avian flu
in China? Mad Cow Disease in the UK? I think I would go with three
tables -- Donors for your general demographics, Donations for a
history of donations and a Quarantine list with countries and dates
that would exclude a donation at this time.

I would first check the date of the last donation to be sure that you
are not giving too much and too often. In the US you get recognition
for donating over a gallon, etc. We want a history in the DB.

Then I would ask "what countries have you visited since << insert
date>>?" One of the options could include the Netherlands, altho the
front end might present it as "None" or something similar to the
donor. When the situation changes, I change the Quarantine list.