addEventHandler ( 'onClientGUIDoubleClick' , root ,
  function ( ) 
    if ( source == yourgrid ) then 
      local aSelect = guiGridListGetItemText ( yourgrid , guiGridListGetSelectedItem ( yourgrid ), 1 )
      if ( aSelect == 'المهمات') then
        guiGridListClear ( yourgrid )
        guiGridListSetItemText ( yourgrid , gridListAddRow ( yourgrid ) , 1 , 'مهمة الديربي' , false , false )
      end
    end
  end
)