Query - Not In

Experts, I have a query that works OK but need to add extra criteria to it.  

In addition to the current criteria I need to remove any occurance where import-CSM2.[Reference Number] is like tblLetterOfCRedit.[BankRef]  

here is the sql:  

INSERT INTO tblLetterOfCredit ( ProjectID, ExpiredYN, LCNo )
SELECT [import-CSM2].ProjID, IIf([Import-CSM2]![Actual Status]="GEC",Yes,No) AS ExpiredYN, [import-CSM2].[Reference Number]
FROM [import-CSM2] LEFT JOIN tblLetterOfCredit ON [import-CSM2].[Reference Number] = tblLetterOfCredit.LCNo
WHERE ((([import-CSM2].ProjID) Is Null) AND ((IIf([Import-CSM2]![Actual Status]="GEC",Yes,No))=0) AND ((tblLetterOfCredit.LCNo) Is Null));

I was thinking that the below might somehow be a solution but I am not all too familiar with Not In or even if the solution calls for "Not In".  I tried it (in the criteria line) but it returned 0 records and it should only remove the one circled below in the pic.

Not In (SELECT [import-CSM2].[Reference Number]
 FROM [import-CSM2] INNER JOIN tblLetterOfCredit ON [import-CSM2].[Reference Number] not like "*"&[tblLetterOfCredit].[BankRef]&"*")

thank you

Here is an pic of the output.  I need to remove the one that is circled.   This record is where  import-CSM2.[Reference Number] is like tblLetterOfCRedit.[BankRef].