jQuery Grid Plugin - jqGrid

I want to use jqGrid with paging and sorting for my asp.net mvc web site. 

My colNames (and therefore colModel) are not known at design time.  They need to be generated at run time.

And each paging of the grid will give me a different set of colNames.

I know that I need to do something like this:

$.ajax({

url: "/Url/To/GetColNamesAndColModels",
        dataType: "json",
        type: 'POST',
        success: function(result) {
               var myColNames = result.ColumnNames;
               var myColModel = result.ColumnModel;

               $("#myGrid").jqGrid({
                        url: '/Url/To/GetData',
                        dataType: 'POST',
                        colModel: myColModel,
                        colNames: myColNames,
                        rowNum: 20,
                        pager: '#myGridPager',
                        viewrecords: true,
                        gridview: true
               });

});

My web service method GetColNamesAndColModels needs to know the sort index (sidx), the sort order (sord), the page index (page) and the page size (rows) as in the standard jqGrid post parameters: (string sidx, string sord, int page, int rows).  How can I can pass such parameters to GetColNamesAndColModels upon paging?