Basically I'd like to use a functions returnvalue as the default value for a field. That however does not work, so I figured a trigger might do the trick.

But how do I tell the table that I only want to update the current record?

-- I didn't expect this to work, and it sure doesn't

ALTER  TRIGGER [MyTrigger] ON [dbo].[T1] 
FOR INSERT 
AS
UPDATE T1 SET F2 =LTRIM(RTRIM(STR(F1))) WHERE CURRENT OF T1

-- So how can I do a positioned update?