CREATE TRIGGER [test_insert] ON [dbo].[myTable]
INSTEAD OF INSERT
AS
declare @str varchar(20)
declare @i integer
set @str = 'T'+left(convert(char,getdate(),112),4)+'00'
select @i=isnull(max(cast(right(rtrim(id),len(id)-7) as integer)),0) from
(select id from myTable where id like @str+'%') a
set @i=@i+1
INSERT INTO myTable
SELECT @STR++cast(@i as char)as id,name from inserted