Formated Serial Number like TS-001

Hi friends , i need to generate a serial number like TS-008 for many entities , So to resolve this i used Triggered , i create a filed (sn) at tebel level & increment this by one. and create one other attribut - varchar through MSCRM. and write trigger like.
Create Trigger "abc"
on table
as
Begin
declare @x as int
select @x = SN from Table where created on = max(createdon)
Upadate table set attrib = 'TS-0' + @x
where SN = @x
end