Is there anyway to accomodate missing dates in a date field? For example, I
want to enter 99/99/99 in a date field to signal that this date was not
provided on the paper form, when entering this data into the database form.
But, if a field is set up as a date/time field, 99/99/99 is not a valid date.
So, it's rejected.

I'm using 9 because the rest of my fields are coded and set up to use 9 to
indicate missing data and we'd like this coding to be consistent. I don't
want to leave the field blank if the date is missing because we want to make
sure that there is an specific explanation for missing data, i.e. it wasn't
that the handwriting was unreadable ("7") or that the individual doing data
entry just forgot to enter it.

Any suggestions?
Thanks.