Dynamically display aoColumns

My Question is related to this one http://www.datatables.net/forums/discussion/13964/create-columns-dynamically-based-on-user-role/p1 .

I Am trying to hide/display columns based on user permissions. I can dynamically control the HTML, but in the .js, since the HTML column doesn't exist, I get an error. Setting bVisible doesn't help because it's still trying to find a column that doesn't exist.

HTML:

<th>Column1</th>
@if (UserCanSeeThis)
{ 
    <th>SecretColumn</th>
}
<th>Column3</th>

.js: (sorry for the dump)

  $('#grdSearch').dataTable( {

            "bProcessing": true,
            "sAjaxSource": uri,
            "fnServerData": function(sSource, aoData, fnCallback, oSettings) {
                oSettings.jqXHR = $.ajax(
                    {
                        type: "POST",
                        url: sSource,
                        data: JSON.stringify(BuildSearchParams()),
                        contentType: "application/json",
                        dataType: 'json',
                        success: function (data) {
                            if (typeof data["error"] == "undefined") {
                                fnCallback(data);
                            } else {
                                alert(data["error"]);
                            }
                        }
                    });
            },
            "aoColumns": [
                { "mData": "SourcePartNumber" },
                { "mData": "SourceVendorName" },
                { "mData": "SourcePartDescription" },
                { "mData": "TargetPartNumber" },
                { "mData": "TargetPartDescription" },
                { "mData": "CrossType" }
            ]
});

When I run this at first nothing happens, then I click again and I get a message that says "DataTables warning (table id = 'grdSearch'): Cannot reinitialize DataTable. To retrieve DataTable object for this table, pass no arguments or see the docs for bRetrieve and bDestroy"