XML input validation

ok, this is goin to be hard...

from the beggining

i have a webservice that returns a xml, that is load to the grid via servlet.
>this is ok, and works pretty fine, let's call this grid as ALL

i have a second grid, let's call it PARTIAL

when i make double click on the ALL grid, i use ALL.deleteRow(ALL.getSelectedRows()); and i copy it to the PARTIAL grid
>this is ok, and works pretty fine

i also have a combo box, and on change event it load's a new xml to the ALL grid
>this is ok, and works pretty fine

now the big problem is:
when i load a xml in ALL grid and there are alredy elements on the PARTIAL grid, i must delete the elements in ALL grid that are repeted, because an element or is in a grid or in the other.

here i have thinked in two solutions:
- catch an after load grid event (i dont know it exists) and compare the elements in the two lists and if equal delete in ALL list.
or
- make some kind of validation in the input, when the xml is loading in to the ALL grid

i dont know if these are common problems, but help is apprecited

thaks in advance

XPATH is the solution

table.setAsync(false); table.setURL("/JudoWeb/servlet/JavaWS.MainX?id=ATLETAS_GRAD&ind_grad="+(index+1)+"&ano=2006");
table.request();
table.setRows("Atleta[XPATH EXPRESSION]"); // set rows XPath