How does Selenium RC recognize SmartGWT Widgets?

Hi,
I am using SmartGWT(Java) and trying to develop a web based application.
I want to use Selenium Testing for that.

Firstly i have used
Selenium IDE and recorded the events which are taken place in the web
page. Before that i have added the user-extensions.js and
user-extensions-ide.js from "smartgwt2.4/selenium/" distribution.
Because SmartGWT widgets can not be recognized by Selenium IDE. The
recorded testcases are now working fine. I have exported the testcase as
Junit.

I am using eclipse galileo IDE. Now i placed the selenium testcase
in a project and i have used the selenium-server.jar for running the
selenium RC from the command prompt. i used like this: d:> java -jar
selenium-server.jar. This runs the selenium RC. Meanwhile i am running
the selenium testcase as junit testcase in ecllipse ide while the server
is in running mode.

But, Now my question is how the Selenium RC will identify the
smartGWT widgets and run the selenium testcases successfully? Do we need to set up "user-extension" for Selenium RC? If the user-extension is mandatory to be setup, What does the "user-extension" consists of? How to run the junit testcase via Selenium RC successfully?

Kindly help me please.

Thanks in advance.