DataGrid Control In Treeview

Question

Hi friends,
 
I should use datagrid control in treeview, in silverlight.There are dataggrids and their textblocks(as headers) which I should use in treeView.When I click related header, related datagrid should be shown. Datagrid data is loaded from database dynamically with my web service methods.But when I try to add data to grid which comes from service method completed event, it gives me the error like 'There is no datagrid like myDataGridNaMe..'
 
How can I reach datagrids in treeview? 
 
If you help me,I will approciate...
Thanks in advance for your replies...