AJaX. Easier if you're using jQuery. But if not, you can manually write your xhr, submit in the background and alert the server response. Or have a hidden div appear with the display.
If anyone knows of a website that can offer ColdFusion help that isn't controlled by neurotic, pedantic jerks* (stackoverflow.com), please PM me with a link.
* The neurotic, pedantic jerks are not the owners; just the people who are in control of the "popularity contest".