ISNULL basically replaces a NULL value with a non-NULL value... the syntax
should be IS and then NULL with a space between.
Unfortunately, SELECT * FROM tblDies WHERE ActualDelivery = NULL doesn't
work... so we have to use IS NULL.
Give that a shot if you have not already tried it.  I did an experiment on
my server and:

SELECT * FROM tblDies WHERE ActualDelivery IS NULL

worked like I expected it to-- selecting all records where there was NULL in
the ActualDelivery field.

Regards,
-Arbon Reimer