I had this same issue not too long ago..

From your Actionlistner implement this code...

try{
getAppletContext().showDocument(new URL(u),"main");
}catch
(MalformedURLException d)
{
System.out.println(String.valueOf(d));}

"u" is the URL of the page  you want in your frame and "main" is the
frame's name...give that a try