onError refers to JavaScript errors, not Drupal form errors. I don't think that would be very useful because it's probably the quote fetching that causes the error, and just repeating it won't help.
I tried putting
<?php
if (form_get_errors()){
// get quotes
}
?>but it didn't work. I think the form errors are reset by the time the page is displayed again.
Joined: 08/07/2007