Use JQuery Datepicker As A Control Parameter For SqlDataSource?

I have the need to display a date in this format: dd/mm/yyyy. This is actually being stored in an ASP.NET textbox and being used as a control parameter for a select on the GridView. When the query is run, though, the date format should change to 'd M y' (for Oracle). It is not working. Can someone tell me what I'm doing wrong? Right now I am pushing the "new" format to a invisible label and using the label as my control param:

$(document).ready(function() {
//datepicker for query, shown traditionally but holding an Oracle-needed format
$('[id$=txtBeginDate]').datepicker({ minDate: -7 , altFormat: 'd M y' });
//get alt format
var altFormat = $('[id$=txtBeginDate]').datepicker("option", "altFormat");
//set date to be altformat
$('[id$=lblActualDate]').datepicker("option", "altFormat", 'd M y');
});