Recently there have been considerable several reports of ¿nanostructured¿ perovskite oxides. In order to obtain detailed knowledge of the factors controlling the formation of these long period structures it is necessary to understand the nature of the underlying atomic displacements and site occupancies. To achieve this goal it is necessary to have the highest quality data, obtained from HRPD, which is the highest resolution neutron powder diffractometer in the world coupled with effective strategies for reducing the number of crystallographic variables. Here we will study Na(1-x)La(1+x/3)MgWO6 solid solutions. The data will be analyzed by treating the structures as modulated structures using superspace crystallography. This approach has been shown to significantly reduce the number of crystallographic variables in complex structures belonging to a number of homologous families.