I know what you are trying to do is possible, but I think it would take me a while to work out how to do it.
Basically, you have to write a javascript.
First, you need to grab the thing they put in the form, and store it in a variable:
ANYWORDHERE = document.forms[0].elements['yourformfieldname'].value;
Then, you need to use "document.write(the name of the variable here)".
document.write(ANYWORDHERE)
I had to do a similar thing for a site I made (
http://referencing.myquestion.net) where you put in details of a book/journal, and it churns out your bibliography entry in the correct format. When you click on a button, it creates a new window with your reference formatted correctly. The javascript actually writes the HTML of the new page itself.
But it took me ages to write - so good luck!!!