You can maybe look at building an array using the ISDATE() Function, or updating a flag field to return invalid entries...

i.e;

You can export the table to a test area, and then create a new "flag" field;

--SET LANGUAGE BRITISH

--SET DATEFORMAT DMY

UPDATE YOUR_TABLE

SET FLAG_FIELD =

(

CASE WHEN ISDATE(YOUR_FIELD) = 1

THEN 0

ELSE 1

END

)