Create a Find Request. Change action to omit. Criteria is just an equal sign =
Performing a find where the criteria specified is put in the field of a related table can produce results different from what you expected.
To find all Donor records where MemCan is "member" that do not have any related Donor records with a value in the Dues::Date field:
Enter Find Mode 
Set Field [ Donor::MemCan ; "Member" ]
Set Field [ Dues::Date ; "*" ]
Set Error capture [on]
Perform Find 
Note the bold face text. If there is one related record with a date in this field and another related record where the date field is empty, this script will include the donor record in the found set.