Hey Amaresh,
I really had a difficult time to automate an application made from ext-
js.
The thing about ext-js is that its filled with dynamic ID's/Elements
which keep changing each time the page is loaded.
So you wont be having a solid object /ID to use in selenium.
I would recommend you to try this method.
Suppose there is a button and it has the following attributes.
-->Element ID - Dynamic
-->Name(Xpath) - Not dynamic
-->Class
I would suggest you to use xpath or u can use the class to get the
Dynamic ID using selenium.getattrubute()..
Let me know if this helped and if we can access the site you are
trying on!
thanks
ro!