Filtering server side data

Hi
I have a table which is populated by the following script. When I click on a row, I can go to another page, in this case "pay_invoices.php" and using the get method, the row id is sent across.No problems here, the code is below

 
 var oTable;
$(document).ready( function () {
    oTable = $('#tbl_purchase_invoices').dataTable( {
        "bProcessing": true,
        "bServerSide": true,
        "sAjaxSource": "datatables_data/purchase_invoice_data.php",
        "aoColumns": [
            { "bVisible": true },
            null,
            null,
            null,
            null
        ],
        "fnDrawCallback": function ( oSettings ) {
            $('#tbl_purchase_invoices tbody tr').each( function () {
                var iPos = oTable.fnGetPosition( this );
                $(this).click( function () {
                    window.location = "pay_invoice.php?id="+oSettings.aoData[iPos]._aData[1];
                } );
            } );
        }
    } );
} );

My problem arises when I introduce the two lines to filter the data returned from the server, below the line starting "sAjaxSource"

 var oTable;
$(document).ready( function () {
    oTable = $('#tbl_purchase_invoices').dataTable( {
        "bProcessing": true,
        "bServerSide": true,
        "sAjaxSource": "datatables_data/purchase_invoice_data.php",
		
		 "fnServerParams": function ( aoData ) {                                                 //THIS LINE 
	  aoData.push( { "name": "company_id", "value":"<?php echo $comp_id; ?>"}, //& THIS LINE
		
        "aoColumns": [
            { "bVisible": false },
            null,
            null,
            null,
            null
        ],
        "fnDrawCallback": function ( oSettings ) {
            $('#tbl_purchase_invoices tbody tr').each( function () {
                var iPos = oTable.fnGetPosition( this );
                $(this).click( function () {
                    window.location = "pay_invoice.php?id="+oSettings.aoData[iPos]._aData[1];
                } );
            } );
        }
	
    } );
} );

When I introduce these two lines, the table stops rendering. I can render the table using the aoData without the fnDrawCallback or I can render the table with fnDrawCallback and no aoData filter, but not together. It is I suspect, a matter of closing braces, but for the life of me and all day spent at it, I'm no closer to sorting it.

Any help would be gratefully received.

David