If you make the page be a form, you can assign the currently displayed text to a textarea, with editing disabled. Each time you click the <emSubmit button, the text is passed back to the cgi script which can invoke the routine and extend the displayed text.

Alternately, you can use Java or Javascript to connect to the server secretly without refreshing the page. Eric Andreychek deescribed soemthing of the sort, OpenThought & OpenPlugin, at the Ottawa YAPC::Canada in 2003.