function showVoucherBox($day,$month,$year,$store_ref)
{
    if($day=='DD'||$month=='MM'||$year=='YYYY')
    {
        alert('Sorry, the date of birth you have entered is invalid');
    } else {
        ajaxbox.open('/store-locator/evoucher?dob='+$day+'-'+$month+'-'+$year+'&store_ref='+$store_ref);
    }
}