Dear Anil,
you can use JSObject to call javascript, but as far as i am concerned, this would not work under firefox. What you can do is use something like
getAppletContext().showDocument(new URL("javascript:setPropertyBoolean(\"submit\",\"disabled\", false);"));
this will allow you to call any javascript function (whether it is built in or you wrote it) inside the form containing the applet. I would suggest using this script for firefox and the JSObject for IE and netscape.
As for submitting the form, surely you can do that...
simply call the document.formname.submit() javascript function, and it would do that for you
ex: getAppletContext().showDocument(new URL("javascript
ocument.formname.submit();"));
Best,
Mohammad