SQL Server - UPDATING TEXT FIELD

hello, 
I have a text column in my database table. I need to update only a part of the text. for example if the text is ,2,,3,,4,,5,,6
i have to only update ,3, with ,10,
so my updated text will be ,2,,10,,4,,5,,6,

i knwo there is function called updatetext that should be used to updating text fileds but i dont know how should i use and what parameters should i pass in my case.

Thanks

these parameters

UPDATETEXT { table_name.dest_column_name dest_text_ptr }
    { NULL | insert_offset }
     { NULL | delete_length }
     [ WITH LOG ]
     [ inserted_data
    | { table_name.src_column_name src_text_ptr } ]


e.g

USE pubs;
GO
ALTER DATABASE pubs SET RECOVERY SIMPLE;
GO
DECLARE @ptrval binary(16)
SELECT @ptrval = TEXTPTR(pr_info) 
   FROM pub_info pr, publishers p
      WHERE p.pub_id = pr.pub_id 
      AND p.pub_name = 'New Moon Books'
UPDATETEXT pub_info.pr_info @ptrval 88 1 'b';
GO
ALTER DATABASE pubs SET RECOVERY FULL;
GO

the above article in books on line but i couldnt get the parameters. I you can explain in detail that would help me 

thanks

Check out the link
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsqlpro03/html/sp03g8.asp
It explains with examples

Initially the syntax is :

UPDATETEXT { table_name.dest_column_name dest_text_ptr } 
    { NULL | insert_offset } 
    { NULL | delete_length } 
    [ WITH LOG ] 
    [ inserted_data 
        | { table_name.src_column_name src_text_ptr } ]


Since our need is to search and replace a text in the entire table, we have to cycle through each row that contains the searched text, get the position at which the text is present, and pass it to the updatetext function, along with its length and the new text the we want to insert. we can use cursor for this implementation

declare @otxt varchar(1000)
set @otxt = 'ExistingText'

declare curs cursor local fast_forward
for
select 
	id,
	textptr(TargetField),
	charindex(@otxt, TargetField)-1
from 
	TargetTable 
where 
	TargetField 
like 
	'%' + @otxt +'%'

The function textptr will return the pointer to the text field 

declare @ntxt varchar(1000)
set @ntxt = 'NewText'

declare @txtlen int
set @txtlen = len(@otxt)

declare @ptr binary(16)
declare @pos int
declare @id int

Finally we can do our search and replace:

open curs

fetch next from curs into @id, @ptr, @pos

while @@fetch_status = 0
begin	
	updatetext TargetTable.TargetField @ptr @pos @txtlen @ntxt

	fetch next from curs into @id, @ptr, @pos	
end

close curs
deallocate curs