In theory that sounds fine, in practice not so much:

Say I have Bull1 associated with Cust1, Cust2, Cust3, Cust4, Cust5. User now opens a UI screen with cust_checkboxes checked for these customers. User then unchecks Cust2 and Cust5. I need to reflect this change in the child table.

So...

DELETE FROM Bull_to_Cust_tbl WHERE BullID = Bull1

for each checked value in cust_checkboxes

INSERT INTO Bull_to_Cust_tbl ...

end for

That's alot of inserts versus a single insert to a main bulletin table with Cust# concatenated. Or is this a false issue - lotsa insert no big deal?