jQuery Grid Plugin - jqGrid

First of all thank you very much fof this awsome plugin. I am really pleased & impressed. I have made a grid with my asp.net project by making datatype: function(postdata) {calling my web services and return json data as excepted}. now i would like to add a subgrid to my grid the same way by calling a web services, and populate the subgrid. I tried all possible way to call my webservices from subGridUrl for no avail. Is there a way to bind the subgrid like i did for the main grid something like subGridUrl:function(id){// Get jasondata; bind it to subGrid; etc}. any help would be greatly appreciated. and thanks again for this beauteful piece of art.