how transform calm ntext domain sql server 2000

so i need transform calm field. conjunction transform matter writetext matter work used below

create list mytable (idfield int, myfield text)
insert mytable (idfield) name 1

declare @data1 varchar(8000), @data2 varchar(8000), @ptrval binary(16)

select @data1 = replicate('1',8000)
select @data2 = replicate('2',8000)

-- sets myfield twine wholly 8000 characters
update mytable set myfield = @data1 + @data2 where idfield = 1 


select @ptrval = textptr(myfield ) 
from mytable 
where idfield = 1 

-- causes an error: crude syntax circuitously '+'.
--writetext mytable.myfield @ptrval @data1 + @data2

how am i ostensible internal variables can't form text? (if i ssql server 2005 i varchar(max) - nonetheless i don't)