String searching

Hi all. I have a problem finding strings that do not exist in a column in a database. I am going to use linq but its more the 'way' of doing I am concerned with.

I have strings like;
MEAL
GPST
EXLEG
EXLG ...etc

I need to find records that does not have this list of strings in, so for example DBML
BUT
sometimes I can have the string MEALDBML, or more concatenated. So this is a known string of MEAL and unknown string of DBML. I would then want to see that record.
I do not know the unknown strings up front, so its a case of feeding in the strings I know are ok, and finding one that are outside that list.
I was also thinking of regex??
Any help will be gratefully accepted.
Scott

ok. Doesn't seem that straight forward.
I think I will create a temp field in a table and and run a replace on known values, i.e. replace with empty string. Anything left will be outside the list and therefore unknown.
Scott