Iframe source change

Hello,

I have a main application window split into two panes. The bottom pane has a embed IFrame.
From a html source opened in the iFrame window i want to change the source of the iframe to another html source on a button click event.

For example: In the main application.js I have
+++++++++++++++++++++++++++++++++++++++++
this.__iframe.setSource("myapplication/login.html");
+++++++++++++++++++++++++++++++++++++++++

on a button click in login.js, I need to set the Iframe source to another html (home.html).
Since Iframe object, which is created in application.js, is not available in login.js I am not able to
do the following,
++++++++++++++++++++++++++++++++++
iframe.setSource("myapplication/home.html");
++++++++++++++++++++++++++++++++++

Can you please let me know how this can be achieved.

Warm regards,
Narasimha