You haven't understood the processing model for XSLT. Your XSLT stylesheet is a program that converts an XML document to an HTML document. Once the HTML is created, the transformation is done and the browser takes over. Nothing done by the browser (or by the user) is accessible to the transformation.
What you can do is to generate dynamic HTML. The Javascript in the generated HTML can then respond to user events and read the contents of text boxes. The Javascript can then pass these values as parameters when invoking a new XSLT transformation, by using the transformation API available in your browser.
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference