[Zope] Passing arguments to ZSQL method

Hi all, I have a problem with variables and namespaces. Here is the problem: I have the following dtml-method (index_html): ... <dtml-call "SQL.update_Cantidad_en_Lin__venta(N__documento=N__documento, N__linea=N__linea, Cantidad=10, N_=N_)"> ... update_Cantidad_en_Lin__venta is a ZSQL method to update a row. If I call the dtml method with: index_html?Cantidad=3&N__documento=ES356&N__linea=10000&N_=GE-RNEW then the field "Cantidad is updated with 3 instead of 10. How can I update it correctly with 10? Any ideas?