how to create Context Sensitive help-By F1 Key press

dubi

I have created a help file with .chm file extension.
I am able to invoke this file when F1 key is pressed.
On doing this only the main page of the help file(.chm) appears.
I like to appear with results of the index words given to it.
For example if I press F1 key when the cursor is on the word 'Context',
the .chm file should appear with index word 'Context'.
All I mean is Context Sensitive help as the Builder environment provide us.All suggestions and comments are welcome.

Thanks with regards.