SQL TRIGGER FOREACH LOOP

I am looking to create a sql trigger that on insert of record creates ultiple records and inserts them into another table.

For instance

Record 1234 gets inserted into table A

Then a trigger runs for after insert

It checks table B to see if record 1234 exists. If it does not then it inserts multiple items for Record 1234 such as

INSERT INTO TABLEB VALUES(1234, 'DOCUMENT A','Y');
INSERT INTO TABLEB VALUES(1234, 'DOCUMENT B','Y');
INSERT INTO TABLEB VALUES(1234, 'DOCUMENT C','Y');

Thanks in advanced.