Forms :: Go-item Not Working?

I hab a button:

flag:=show_lov('lov16');
if :block.cliente_no is not null then
go_block('clientes');
execute_query;
go_item('block.codigo');
end if;

it calls a LOV and return a value to :block.cliente_no, then execute a query in block clientes, but cursor doesn`t goes to block.codigo it remains in the button ! Why doesn`t works ? Note: if I insert a message before line go_item('block.codigo'); cursor goes to 'block.codigo' (message('hallo');