If an exists filter is the answer, it will probably look something like
this: EXISTS:a:$$EXISTSMOD=NOTEXISTS EXISTS:a:$$OBJCODE=TASK
EXISTS:a:projectID=FIELD:ID EXISTS:a:DE:= The first
three lines should be correct as-is -- you're looking for something that
is task-related, and will not exist, in your project report. The fourth
line is what you would need to fill out, with the name of your field and
answer you're not looking for. (remember to preface that name with a
"DE:")