Using "Contains" in a trigger

I have a trigger that audits changes by posting to an audit table when changes to other tables are made.  It works great; however, now I must isolate this to happen only to those records where the travelrequest_no field contains "-U-" while ignoring the other records.
I put a
WHERE CONTAINS(travelrequest_no, '"*-U-*"') after the FROM line below.  The trigger is successfully saved, but does not execute when I insert new records.  What am I doing wrong?  Perhaps another way of doing this?
--------------------------------------------------code---------------------------------
CREATE TRIGGER AuditVisit ON dbo.tbl_travelrequests
FOR INSERT
AS
/* * INITIALLY SETS THE TRANSFER FLAG OFF AND INSERTS OVERALL LAST MODIFICATION DATE IN 'tbl_auditForTransfer' */

BEGIN
   INSERT INTO [dbo].[tbl_auditForTransfer] (travelrequest_no, LastModifiedDate, TransferFlag)
   SELECT travelrequest_no, getDate(), 'OFF'
   FROM inserted
 
END




Thank you,
Jayme