>>>>Do you want to have a trigger firing when a new column is added?
>>>Yes
>>> In SQL Server 2005 you need to look at DDL triggers.
>>>Why?
>>>
>>>Viv
>>>
>>>
>>Why not? DDL triggers are supposed to fire when the structure changes - looks like your case.
>No - structure doesn't change. It's just an INSERT into the ProductFileColumns table.
>When that happens I need to add a record in ProductFileData for each existing row using the Id of the newly inserted column.

Aha, when what seems to be a problem? Just write a simple AFTER INSERT trigger.