Is there a way to fill blank fields with default values while appending data to a table?

Solution: While viewing a table in the data sheet view, move all the fields anticpated to be blank to the right and paste append only the fields with data. Then the blank fields are not written to and they are populated by their default values.

So you are not actually doing an append - rather copy paste.....

If you are doing this from Excel watch out for a security update that seems to pitch up once a year from MS that stops you from being able to do such...
Just FYI if you are realeasing to an external party

Thanks for the heads up dcb! I am pasting the Excel data using "Paste-Append" from the table's File menu.

in the design viw enter the default value and also required to yes.

design view of the table enter the default value. enter yes in the required property.

if you fill the table from another source setting the default value won't help.
after you finish filling the table run a quick Edit Query and edit all empty fields to the default value you want.