iphone - inserting the value in to a perticular node in xml file -

i have got problem in inserting value in xml can me please. new iphone development in situation have got xml .....

 <group name="electrofusionboxdata">         <item name="electrofusionacquire" type="barcode" usereditable="y" description="start electrofusionbox data" minquantity="1" maxquantity="1" allowedvalues="">xxxxxxx<actualvalues />         </item>         <item name="weldnumber" type="integer" usereditable="y" description="weldnumber day" minquantity="1" maxquantity="1" allowedvalues="">xxxxxxxx<actualvalues />         </item>    </group>  

from above xml parsed 2 elements , displayed in tableview "electrofusionacquire" , "weldnumber" 2 fields created 2 textfields . when user entered data in textfields text needs save in place of "xxxxxxxx" above xml please suggest me way achieve this. in advance.

i assuming using nsxmlparser parsing xml, read parser. writing/modifying xml need use other parser gdataxml or touchxml. need use xpath queries accessing particular node , updating values