create table a (pk int identity(1,1) not null, orderby int, field nvarchar(255))
go

insert into a (orderby,field) values (12,'001')
insert into a (orderby,field) values (14,'002')
insert into a (orderby,field) values (5,'003')
insert into a (orderby,field) values (8,'004')
insert into a (orderby,field) values (15,'005')
insert into a (orderby,field) values (13,'006')
insert into a (orderby,field) values (10,'007')
go

create procedure SeekRecordByNum
@num int
As
DECLARE @PK int
DECLARE @Sql nvarchar(255)

If @num>(Select Count(*) from a)
BEGIN
Select * from a where 0=1
RETURN
END

Set @SQL='Select TOP '+CAST(@num as varchar(13))+' @PK=PK from a order by orderby'
execute sp_executeSQL @SQL,N'@PK int OUTPUT',@PK OUTPUT

Select TOP 1 * from a where PK=@PK
Go

exec SeekRecordByNum 1
exec SeekRecordByNum 2
exec SeekRecordByNum 6
exec SeekRecordByNum 100

drop table a
drop procedure SeekRecordByNum